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have the driving power, I will then give you the information how to proceed.-W. J. LANCASTER. [34056.]-Waves of Light and Heat.-The paper referred to is probably that on "An Experimental Verification of the Velocity of Transmission of Radiant Heat." The author merely proposed to show that, so far as his experiment went, the velocity of radiant heat is identical with that of light. The paper was somewhat sharply criticised by Professor Forbes and others, who showed that there was a fundamental error in the mode of experiment.-J. BROWN, Belfast.

[34057.)-Electric Light.-The best apparatus you could have for the purpose of obtaining two lights would be one of Siemens' machines; the cost of such an apparatus, including lamps, wire, and all necessaries, would be about £150. A band from the engines would drive this without any cost. A couple of horses or so would not, I imagine, make any difference to an ordinary 500 horse engine. Now, as to lamps, I am almost inclined to think the candle would answer every purpose. They work well, the cost is low, and the light is good. You might have half a dozen candles connected, one in each cabin, and one in engine-room, and the others where required. The cost of the candles is 7 d. each, and they burn for from 1 hour to 1 hour each. The light obtainable from 4 candles would be about equal to 4,000 candles, or 1,000 candles each. Of course, you can have an automatic lamp to use up all the earrent, thus obtaining a single light very brilliant. There would be but little cost in keeping the apparatus at work. I would have the machine in the engineroom, and the engineer could, with scarcely any trouble, keep it in order. A Gramme machine would answer, but it costs more than a Siemens.-W. J. LANCASTER.

[34057.)-Electric Light.-Gramme's is the best system at present. A machine would cost about £130, the lamps on Serrin's principle about £20 each. The cost for maintaining as power is supplied would be very small, and the cost of the light would amount to the cost of the carbons, and this again depends on the power of the light desired. The querist should read Fontaine's "Electric Lighting," as translated by Higgs, and published by Spon and Co.-SEARCH.

[34058.]-Microscopical Manipulation. Get the work, by Dr. Carpenter. "The Microscope," and work through the whole of its chapters, taking up one chapter at a time, and working at it until you have mastered all its details (plenty of work for you). Thus, beginning with "Microscopic Forms of Vegetable Life," you will find 100 pages of most interesting matter about vegetable cells, desmids, diatoms, &c., which will occupy fully two to three months to familiarise your mind with their origin and construction, then you will go on through successive chapters until you come to the study of the higher animals, and when you have done all this well, you will be a microscopist of no small degree.-W. J. LANCASTER.

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[34060.1-Surveying.-"A Sub." will find the

be a suitable work for a beginner to study. It is Treatise on Surveying" in the Weale's Series to edited by Edward Nugent, but written by T. Baker; the cost is 2s.-T. E. J.

[34061.J-Electrotyping Ferns.-The very best thing. I have produced very fine things with the means I recommend. In 'Smee's Electrometallurgy "there is a description, as far as I recollect. It is a nice job, and requires neatness.-ANGLODANE.

34061.]-Electrotyping Ferns.-Let the back of the leaf be carefully imbedded in a paste of plaster of Paris, and with a piece of wood guide the plaster so that it may fill up every crevice that is not to be copied. When the plaster is quite hard, melted wax may be poured over the leaf (which should be dusted over with plumbago previously to prevent the wax from adhering), and allowed to remain until quite cold. The leaf and plaster should now be separated from the wax mould, which is then ready to receive the plumbago, and to be electrotyped in copper in the asual way, after which they may be gilded or plated at pleasure.-W. G. H. A.

[34061.]-Electrotyping Ferns.-Dip them in a solution of phosphorus in bisulphide of carbon, from that into a solution of nitrate of silver, let them dry, and give them a dip in chloride of gold solution before putting into the sulphate of copper bath. When slightly coated (and mind the coat must be very thin), remove, and plate or gild in the usual way. Skeleton leaves do not answer.-T. B. [34062.]-Cementing Cork to Metal and Glass. -Good indiarubber solution will do if both surfaces are flat.-T. B.

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[34065.J-Polishing Object-glasses.-First use rough emery until the lens is in form, then gradually use finer emery, until you have the finest washed emery; use this until not a scratch or mark is to be seen, but only a dull polish. Then polish with putty powder on a pad glued inside the tool. Of course, LANCASTER. this refers to grinding and polishing a lens.-W. J.

[34066.]-Electro-Magnet.-Wrap on the poles as much No. 16 gauge covered copper wire as will make a bobbin on each 3in. long and lin. diameter from circumference of poles. The bobbins will be 3in. long by 3in. Make them both alike, and you will obtain the best effect you can get from the electro-magnet.-W. J. LANCASTER.

[34066.]-Electro-Magnet.-I would advise you to wind your magnet with about 4lb. of No. 14 cotton-covered wire on each leg. This will give you about 7 layers of wire 6in. long. I would further advise you, when using this with the battery you name, to connect the battery up in two series of 5 cells each, thus lowering the internal resistance of battery to what it should be if all the cells were joined in series. With a magnet such as you describe you should be able to sustain about 6cwt, when fully excited. I purpose giving the particulars of some experiments with large electro-magnets shortly in the ENGLISH MECHANIC.-OHM.

[34068]-Hot Bath-To MR. LANCASTER.-1. The bath should be made of either copper or iron. I would prefer the latter. Make it the size you require. Then (2) use linseed oil. This boils, however, at 602° F., but under pressure it will not boil until you have a higher temperature. I should prefer linseed oil to anything else I know. 3. I am afraid not. The best source of heat would be a Bunsen's burner with a rose head. The supply of gas can be so easily regulated, and a mercurial thermometer could be inserted in the oil, and left there, as the mercury would not boil until 60° F. above the boiling point of the oil. 4. Any of the ordinary glass flasks, bath without any danger of fracture, and you will tubing, test tubes, &c., will stand the heat of this find it possible to regulate the supply of heat so nicely that the bath will not alter a degree for 10 to 12 hours.-W. J. LANCASTER,

[34068.]-Hot Bath.-" Bath" does not mention the temperature. Fasel oil gives a temperature of 270°; spirits of turpentine, 320°; melted paraffin, a temperature varying from 212° to 400°; isoterebenthene-prepared by heating oil of turpentine to 480° for some hours in a closed vessel-a temperature of 350°; olive oil, 500°; colophene-obtained by digesting oil of turpentine in the cold with a small proportion of sulphuric acid-a temperature of 600°; metaterebenthene-obtained in the same way as isoterebenthene-a temperature of 660°. A spirit lamp with a large flame will give a temperature of 1,000° Fahr. always used for operations where much heat is The German glass is noted for its infusibility, and required; the English glass contains too much lead to render it useful in such cases. Glass about 1-10in. thick will stand a pressure of 50 atmospheres.-T. EVANS.

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[34071.]-Brown Paint used in Carriage Painting.-I think what "Young Painter" wants in the shape of purple brown is a lake colour.-JACK OF ALL TRADES.

[34072.]-Amateur Confectionery-Sugar Boil. ing-If you use tartar for boiled goods they must be kept in air-tight packages. See my letters on Confectionery" in the ENGLISH MECHANIC Some volumes back.-L. W. D.

[34073.]-Electric Lighting.-You cannot make a simple electro-magnetic machine for the purpose of lighting your workshop. You can make a machine, which will cost you about £50 to do the work fairly well, and if you care to spend so much, I will give you sufficient instructions to enable you to make such a machine.-W. J. LANCASTER.

[34073.]-Electric Lighting.-All the machines that would be of any use are patented. You should use a small Gramme with Jablochkoff's new machine for giving several circuits with his candles. This arrangement leaves little to be desired.—OHм.

machine described in a previous volume of the [34073.] Electric Lighting.-The "brush" ENGLISH MECHANIC is the simplest form, as is also the lamp. Description would be impossible in the pages of this journal. Advertise your address.SEARCH.

[31075.J-Solvent for Hair.-I have a memoput it into a saturated solution of caustic soda, and randum to the following effect: "To dissolve hair, boil." Now, I never remember making the experiment, but I believe it to be true.-W. J. LAN

CASTER.

[34062.]-Cementing Cork to Metal and Glass.
-1. Melt 5 parts of black resin, 1 part of yellow
wax, and then stir in gradually 1 part of red ochre
or Venetian red, in fine powder, and previously well
dried. This cement requires to be melted before use,
and it adheres better if the objects to which it is
applied are warmed. This is not so good as, 2,
mastic cement, which is made by mixing 20 parts of
well-washed and sifted sharp sand with 2 parts of
litharge and 1 of freshly-burned and slaked quick-patent ventilators put into my chimney, close under

[34075.]-Solvent for Hair.-Caustic potash. It
is also a solvent for human skin. I think most
things that would do one would do the other.-T. B
[34076.]-Ventilating a Bedroom.-I have had

lime, in fine dry powder. This is made into putty the ceiling, and have had them removed, as, at

opening and shutting. If I required ventilation I should get it through an outer wall, and not into a chimney.-J. T. F.

fire burns briskly when the door and windows are [34076.]-Ventilating Bedroom.-If "L. D.'s " closed, and he is not troubled with smoke, he may venture-not otherwise.-JACK OF ALL TRADES.

[34076.]-Ventilating Bedroom.-Dr. Arnott strongly recommended the plan you mention when the chimney-throat over the fire has been daly diminished à la Rumford: he also designed a balanced ventilator valve that only permitted of a current out of the room into the chimney, and closed against a current of smoke from chimney into room. To prevent draughts a fair-sized air inlet should be made in wall between bedroom and passage, I think, to duly supply fresh air to room.-F. W. S.

[31077.]-Gum Paste.-1. The quantity of gum to 1lb. of sugar will differ materially, according to the amount of water put to the gum. It should be the stiffness of shoemaker's paste; before adding to the sugar add a dust of fine starch, and mix it to the consistence of stiff dough. 2. Dust the moulds with fine starch. 3. Take out immediately or when the paste takes the impression, cut off the rough edges, damp the edges, and fix in the desired positions. If this is not what you want, write again.— L. W. D.

[34078.]-Coke for Chilling.-This is the first time I ever heard of a special coke for chilled goods. There is a great difference in iron for chilling. The chilling is done in cast-iron moulds in some cases, jacketed with water space and water.-JACK OF ALL TRADES.

the principal dimensions of the 7' 7" coupled engine: [34082.]-Engines at Paris.-The following are

Length of grate

Length of internal fire-box... Width of internal fire-box

ft. in. 7 9

No. of tubes, 206; external dia., 1'92 Length of tubes Heating surface of tubes

7 0

36

11 6 1,230 sq. ft. 91-5 29

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fire-box... Total

Mean diam. of boiler... Diam. of driving-wheels Diam. of leading wheels

Total length of boiler Cylinders, 173" diameter x 25" stroke; centres of cylinders, 6' 11"; centre of driving-wheel to middle wheel, 8' 23"; centre of middle wheel to leading wheel, 9'4"; length of connecting rod 8' 101". Weight on leaders middle drivers

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11 tons 133 12

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They run very steadily at 55 miles an hour.E. L. P.

[34086.] Steel Manufacturer. Huntsman's similar to that used by brassfounders, which is got process was to place 10 or 12 crucibles (made for the purpose to hold about 34lb. each) into a furnace to a white heat with a coke fire, after which he charged them with pieces of bar steel (weiging about 1lb. each) specially hardened. When the pots were full he placed the lids on, filled the furnace with coke, and put the cover down. As the furnace required feeding the workmen watched the progress the metal was making, and after three hours' melting it was run into ingots.-C. J. BONSER.

[34087.]-Hardening Gravers.-Heat in charcoal dust (not too hot), and plunge into a box of wet yellow soap. This renders the end of the graver very hard and very tough. I have had to alter the shape of gravers, and bend them sometimes, for awkward jobs. When in the provinces I took this out of an old book. published some 40 years since, and it stood me in good stead many times.-JACK oF ALL TRADES.

lowing is an exceedingly simple way of making [34089.-Single Needle Telegraph.-The fol

B

D

by mixing with linseed oil. It sets in a few hours, times, the smoke came out and the ceilings became single needle instruments; it has several defects, having the appearance of light stone.-C. C. HAWK. blackened. The ventilators had self-acting lids but its simplicity renders it very suitable to those

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find out what electricity really is.-J. BROWN,
Belfast.

not experienced in making electrical instruments :-
In the annexed diagram A is a magnetised needle,
made of watch-spring steel, and suspended by a pin
[34106.]-Bichromate Battery.-The zinc and
passing through a hole in its centre; B, an electro-sulphuric acid react as usual, liberating nascent
magnet made of a piece of soft iron about in. thick, hydrogen. The bichromate and acid react so as to
and 3in. long, bent to horse-shoe shape, and coiled produce either free or nascent chromic acid; the
round with three layers of No. 16 copper wire (cotton hydrogen reacts on this by taking up oxygen and
or silk covered); C, commutator, made of four strips reducing it to the sesquioxide, which in turn forms
of brass, 1 and 2 spring up against 3, and may be a sulphate of chromium, and uniting with the
pressed down on to 4; D, battery, Daniell or sulphate of potash formed in the first decomposition
Léclanché. The diagram shows the connections. Of to chromic acid, constitutes chrome alum. This
course, if you want to communicate from one place series of reactions may or may not occur, for the
to another, you must have two instruments. The process may be traced out in several ways, but
signals are made by pressing on the strips 1 and 2, the result is the formation of sulphate of zinc and
which deflect the needle. For further information chrome alum. As to the last question, it is a
as to winding the magnets, making the batteries, mistake: the zinc does require amalgamation, but
learning the alphabet, see back numbers of the amalgamation does not greatly protect the zinc when
ENGLISH MECHANIC.-C. DETAILLE.
worked without a porous cell any more than it would
with nitric acid, because the liquid removes the film
of adhering hydrogen which is the effective protect-
ing agent with the amalgamated zinc in ordinary
acids.-SIGMA.

[34089.]-Reading Single Needle Instrument. -If you only want to learn the code, you may make up a model instrument directly with but little trouble. First, cut out a piece of cardboard, size required for front, then make a wooden frame so that that it will carry a needle and two spools-old cotton spools will do; one of them must be fixed to the back of the handle, the other to the spindle carrying needle. Then two tacks must be fixed in each spool, and a piece of elastic tied from each tack to the corresponding one on the upper spool. You will thus have an instrument corresponding to a needle instrument, and you will be able to learn the code by using it, as well as if you had an expensive instru. ment, the whole cost of the above being under 6d. Now, when having learned the code sufficiently to read off at once, I would then make a pair of good needle instruments, and I shall be pleased to give you instructions how to make them.-W. J. LAN

CASTER.

[34107.]-Writing on Brown Paper.-Why not
purchase a wrapping paper already rolled or glazed ?
Most of the wholesale stationers would give sample
and price on application, as this kind cannot actually
be procured at retail shops. But perhaps "Seeds.
""
man might get over his difficulty by trying a quill
pen on his ordinary brown paper if he has not
already done so.-C. LARK.

[34107.]-Writing on Brown Paper.-Size it with Young's patent size. Melt the size and apply with a brush.-SAMUEL SMITHER. [34108.]-Batteries for Telephones.-To MR. W. J. LANCASTER.-The simplest way to make a sulphate of mercury battery is to have a small jar about 3in. deep by 2in. diameter, then a cylinder of zinc about 1in. diameter, and a porous cell 1in. [34099.] Bone Cracking Extraordinary.This ought not to be the case. The two bones of the diameter. In this cell have a carbon rod about in. fore-arm, the ulna and radius, should move noise- diameter, and around it small pieces of carbon, lessly at their points of articulation with the while at the bottom, and in the interstices of the humerus. If, therefore, any noise is heard, such as carbon pieces, put a quantity of mercuric sulphate, cracking every time the arm is moved, my opinion of then fill up with water. In the outer cell use a the cause is this: The too frequent strains upon the strong solution of salt. This cell would be of use on ligament of the arm (as an athlete) have caused a telephone wire to work a call-bell, but it would them to lengthen without a corresponding thickening. not be of any service used with the telephone. The Hence, the ulna does not move perfectly in the electro-motive force of Grove's, Daniell's, and humerus, and, consequently, springs into its place, Léclanché's bear the proportions to each other of 10, producing the noise referred to. The radius would 56, and 77. A good call-bell can be made up with not be so much affected as the ulna, and I should put a small electro-magnet, and vibrating armature at the whole of the noise down to the ulna. Again, the each end of the line, a small button closing circuit cartilage in which the ulna moves might be comat will. The electro-magnet should be made out of pressed from too great a strain in practising gym-in. soft iron. A piece 4in. long will make a good nastics, &c., to too great an extent. The only magnet. Bend it into the form, and heat it to a red remedy which presents itself to me at the present after being bent, then make two boxwood bobbins moment is rest, and that a continued one, until the to go on the poles, and about 6in. long each one, symptoms have disappeared. The same remarks and having about 14oz. of 22 covered wire on each. will apply to the femur and the tibia only of the leg. The armature should be made of thin iron 2in. long -W. J. LANCASTER. and in. wide, with a spring at one end and a wire at the other, carrying the hammer. The point and opposite part of spring should be tipped with platinum.-W. J. LANCASTER.

course it is impossible in arithmetic, as we do not deal with negative quantities, to subtract a larger number from a smaller. If in the fractional part of the formula the letters are reversed in the denomi nator-that is, L E instead of E-L-a not improbable result is obtained to the question in this case-1 in 46'6. To allow the full tubs to balance the empty ones the incline would be necessarily very little removed from a level, while the frictional resistance of both sets, rollers, &c., would have to be in excess of the gravitating power of the full set, which is the sole motive agent. Another formals is given by the "Pocket Book" to determine the inclination at which the resistance is equal in both directions, which condition of things would form an equilibrium. Now, this is what is required in the first formula so that it would appear to obtain the rate of inclination which would form an equilibrium. Two formulæ are given which do not give the same results.-T. E. J.

[34124.1-Wind Vane.-The larger part of the vane is blown around by the wind, and thus is kept in position. The arms are so made as to cut the wind as they come down, and be lifted by it upwards. If you get one of the penny toys having four arms like a windmill, and watch it, you will understand the motion better than by reading answers. The direction you will find in the case of the soldier vans is due to the larger half of the soldier being on one side of the centre of rotation.-W. J. LANCASTER

[34127.]-Polishing Agates.-Truly this is a labour of love. Never do I remember working much harder than when, as a student of geology, I rubbed down and polished numbers of ammonites, nautilus, belemnites, rook crystal, agates, &c. Now, I have since found a much easier method of rubbing them down, and that is to take the mineral to a lapidary and get it cut into plates. This wonderfully lessens the labour, and I would recommend you to do the same. Then to polish them: Proceed in the manner I have described for polishing glass, answer 34065, working carefully during the latter part of grinding with the finest emery. It will also take you a long time to get a good polish, but you must remember one thing-namely, the longer it takes to produce a polish the longer that polish will last, and vice versa.-W. J. LANCASTER.

[34128.]-Hard Water.-Boil it before using, and add as much washing soda as you will find by experience answers best. By doing this you ought to make it as 'soft as you want it.-W. J. LAN• CASTER.

[34131.]-Gold Bath. It is very doubtfol whether you will ever see your 4oz. of geld again. Add sulphuric acid to your solution until effervesence has ceased, collect the precipitate, and pour it in a crucible with a little potash. The acid should be added gradually, and in the open air.-03.

[34131.]-Gold Bath.-Place the gold solution in until effervescence ceases; this will form a precipi a large vessel, and pour in gradually sulphuric acid tate. The operation should be performed in the open air, as the fumes, if breathed, are very dele terious. Wash the precipitate in hot water, after which it may be dried, mixed with a little potash, and fused in a crucible until the gold is gathered in a button.-W. G. H. A.

[34131.]-Gold Bath.-Precipitate the gold by means of an acid, then fuse the product in a crucible.

[34115.]-Spongy Iron.-I believe this is being
produced on a fairly large scale in England by the
American Blair direct process, from rich hæmatite
ores. Mr. Ireland, of Manchester (Mr. Blair's
English representative), read an interesting paper to
the Iron and Steel Institute, at their last meeting, on
this plan of utilising Indian ores with the somewhat
indifferent Indian fuel, alone available commercially-ELECTRIC.
Prof. Bischof also produces spougy iron for his
excellent filters, doubtless on a commercial scale.
Fusion, I should imagine, is the one thing to be
avoided, and as ore is reduced at comparatively a
low temperature, fusion ought not to be approached
to even.-F. W. S.

[34132.]-Gilding Battery.-The battery is not in fault. Use your solution warm, and reduce your battery power.-ELECTRIC.

[34102.]-Stone Breaking Machine.-"Wan: derer" will see these advertised very freely, and each maker or patentee claims that his special design is best. I have had to go into the subject, and am of opinion that the early Blake machines were very good ones for mere road metal work, but that Marsden's improved later machines enable them to hold their own with the later patents, unless I except Hall's (a foreman of Marsden's). This, I think, is even less likely to get out of order than the original machines, as it divides the strains, which are necessarily very variable, consequently trying to the strongest machinery. This latter machine, however, would be difficult to meet second-hand, whereas the older Blake is often on sale at machine brokers, &c., at a very reasonable price. Marsden makes small machines for small requirements, which only require a couple of labourers to work them, and are easily transportable to any part of the roads under repair. It may interest "Wanderer" to know that 1in. metal makes a sounder and better road than 2, the usual size, although costing more to make in first instance, and McAdam, I believe, always rejected all small." Macneill (Telford's assistant), I believe, made his best roads with a bottom foundation 6 or leaves the eggs or germs, on which it has no effect. consist in getting the colour light enough. After Sin, thick of concrete, 1 cement, 1 sand, and 8 gravel (or the "small" above referred to), on this 3in. of

broken stones.-F. W. S.

In the cell zinc is the positive metal, and copper the [34105.]-Positive and Negative Metals. negative-that is, the current is said to flow from the zine to the copper in the cell, and upon this theory it is evident the polarity is reversed outside the cell, the current then travelling from the copper to the zinc. Thus, the electrode from the copper is positive, and from the zinc negative. Students often confound the terms, and it really is unfortunate some other and simpler nomenclature cannot be adopted.-W. J. LANCASTER.

[34105.]-Positive and Negative Metals.-The whole battery must be regarded as a circuit, in which any part from which positive electricity is flowing is a positive part in relation to any other to which the electricity flows. Hence zinc is the positive metal, because positive electricity flows from it to the copper plate through the liquid. The wire connected to the copper plate is the positive pole, because positive electricity flows from it to the wire joined to the zinc plate. The latter wire is thus the negative pole. A distinction must be drawn between the words pole and plate. Of course, the idea that electricity is a fluid or current is merely a provisional assumption on which to hang our arguments till we

[34121]-Moths in Furniture.-Give the furni. ture a good brushing, taking care to brush out well the crevices.-TELESCOPE TELE.

[34132.]-Gilding Battery.-Most probably it is the solution at fault, not the battery. Insufficiency of surface of anode in proportion to that to be gilded, solution not hot enough, or not enough cyanide, would be amongst the most likely causes of 15 lightness of colour.-W. G. H. A.

[34121.]-Moths in Furniture.-Moths are most troublesome things to get rid of, especially in fur. [34132.]-Gilding Battery.-Your bath may niture. Sulphur will not easily kill them-it only give a light colour, but I cannot understan stupefies them, or at best destroys the moth, and giving a brassy colour. My difficulty was wont to to spring up again next year. The same is true of you have finished, and finally scratch-brushed the different insect-destroying powders, all of which the work, return it for an instant to the bath. This fail to destroy the germs. The only effectual mode sometimes gives a very good tone to the colour, and as carried on by professional moth-exterminators.tities are used for making cyanide of potassium for of destroying them is by a process of fumigation, is very useful for filigree work.-Os. UPHOLSTERER.

[34122.]-Connecting Clock with Electric Bell.-The simplest way to do this is to connect a wire to the arbour in which the hour finger works, then have a movable arm, easily adjusted, so that when the hour finger reaches, say, seven o'clock, it rides upon the arm for, say, five minutes. The arm should not be too strong, and should be connected to a spring, so that the finger will not be bent or displaced by passing over it. The other parts of the apparatus will be, of course, the batteries, line wire, and bell. I have recommended that the finger should ride on the arm for five minutes. This is to insure contact, as it might probably in time get a little dirt upon it, and you would not always wake at the same moment, and you could stop the ringing the moment you got up. Besides, the very fact of your knowing the bell would ring five minutes would cause you to get out of bed to stop it, and nothing could wake you better than this.-W. J. LANCASTER. [34123.] Mining.-To "T. E. J."-I imagine there must be some error in the formula given in the "Colliery Manager's Pocket Book," for of

[34133.]-Prussiate of Potash.-Large quan. electro-plates, photographs, &c. I believe it is used in conjunction with sulphate of iron to produce the common washing blue as used in the laundry. ELECTRIC.

[34135.]-Pediment Barometer.-Remove the mercury from the tube, then boil it, and filter two or three times, and fill into tube again, taking cars that you expel all air bubbles before putting the tube into the case again.-W. J. LANCASTER.

[34137.]- River Thames Steamboats.-The dimensions of the Princess Alice and Albert Edward are, as far as I can remember, 219ft. long, 11ft. 6in. wide, and 8ft. 4in. deep. The engines oscillating, cylinders 44in. bore, 45in, stroke, fore and aft of the shaft, both piston rods working on the same crank air-pump between the cylinders under the shaft. do not think the boats are wide enough to get the ordinary form of engines in. The Alexandra has been running regalarly all the season, but I do not know anything about the Palmerston, Albert Victor, or Oriel. There is an Oriel now running, but it is s long time since I have seen the Sibyl. If Murano"

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will get a time-table he will find a list of all the
company's boats. Two new ones, the Osprey and
Princess Mary, have been built this year for the
Westminster and Woolwich trade, and are larger
and more comfortable than the old ones.
engines have separate expansion valves, and link-
motion reversing gear, instead of the awkward levers
and loose eccentrics.-H. W. W.

The

smalls. I shall be glad to give more information if necessary to "H. J. A."-C. C. HAWKS. published by Davy and Sons, Long Acre. It begins [34148]-Hall Marks.-See Chaffers's work, its dates with the years 1438 9, and has a large plate of fac-simile stamps, price 12s. Along with this procure "The Book of Hall Marks," by Mr. Alfred Lutschaunig, the manager of the Liverpool Assay [34138.]-Silvering Thermometer Scales.- Office, price 6s. This book has the date, letters, and You must first well clean the scale with fine emery fac-similes of all the marks of all the halls, paper, then swill off any bits of brass that may be beginning with Sheffield, 1773. It has, also, actualleft, and proceed to silver the scale in the following size engravings of watch-cases, with the date, letter, manner: Make a strong solution of nitrate of silver and other marks in their proper places. In addition ay 60 grains to an ounce of distilled water, then to these there is a vast mass of information, both aid common salt slowly until no precipitate is legal and otherwise, and the book is a companion formed when small particles are again added, then that no person, whether dealing in the precious stop the addition of salt at once, allow the precipi- metals, or simply desirous of such knowledge, tate to settle, filter to collect the precipitate chloride should be without. I do not know where it can be of silver, then mix with it three times its weight of bought, but the author would, no doubt, give that cream of tartar, and put a portion on to the scale information. Any attempt to give a satisfactory with a little water, rubbing it up and down the scale answer here would be mere nonsense, and only with a cork. When done put under a flow of water," fog" the reader. Chaffers's is the ancient, and then into sawdust until dry, afterwards lacquer it Lutschaunig's the modern vade mecum.-STYLUS. with a colourless lacquer.-W. J. LANCASTER. [34147.]-Gelatine Plates-Ferrous Oxalate. [34138.]-8ilvering Thermometer Scales.-A-Formula: neutral oxalate of potash, loz.; hot very good method has been given, but no one seems water, 4oz. When dissolved, add of ferrous oxalate able to use it-viz., a solution of silver in hypo- oz., shake the mixture well, and when cool filter sulphite of soda. Dissolve, say oz. of nitrate of for use. Shorter exposed plates must remain in silver in distilled water, say a quarter of a pint, now longer. It cannot be "varied for different exposures dissolve 4oz. of hyposulphite of soda in half a pint of and for plates of different rapidities." For this you water, now add this latter to the solution of silver must resort to alkaline pyrogallic acid development. until the precipitate which forms is re-dissolved. You should dry your plates in a drying-box.-W. J. There may be a little black flocculent matter which will CHADWICK. not dissolve, but you can easily see when the silver (34148.)-Highland and Great North of Sootbas disappeared, then make up the solution with land Engines.-All the engines used by these comwater to one pint, in order to receive the deposit. panies (except a few shunting tanks) have outside The work should be well polished, free from grease, cylinders. The engines now chiefly used for passenger and wet. Sling the scales on a piece of thread or traffic on the Highland main line (Inverness and wire, and dip them into the solution. I have Perth) were built by Dubs and Co., in 1874. They sbtained very good results with this method. The have bogie carriage in front, and the driving wheels, work should be washed in clean water, and dried in 6ft. in diameter, are coupled. The cylinders are 18in. warm boxwood sawdust.-Os. x 24in., and are inclined after the pattern of the old Crewe engine. They have outside framing, flush top boiler, with dome in the middle of the barrel, and safety-valve on the fire-box. Some are furnished with a steam-brake. The cab is larger than is generally used. The older Highland engines are built by Sharp and Stewart. The passenger engines made by this firm were 6ft. singles, with raised fireboxes, and Allan's safety-valves. The traffic, especially in the tourist season, became too heavy for them, and several were turned into coupled engines. Those which were not are still used in winter and spring, when the traffic on the Highland line is comparatively light. The goods engines have two pair of coupled wheels, 5ft. diameter; the size of cylinders is the same as that of the bogie engines. They have also their fire-boxes raised, with one of Allan's safety-valves on the boiler, and a dome sur. mounted by a safety-valve on the fire-box. Some of the bogie engines are also used for goods traffic. The Highland engines are painted exactly the same colour as the L.B. and S.C.R. The majority of the G.N. of Scotland engines are bogies. The latest supplied to the company were built by Neilson and Co.; the older ones are by Stephenson and Sons. The former are much heavier than the latter. They have outside framing; cylinders, quite horizontal, 18 x 24, and driving-wheels 5ft. 6in. coupled. None of this company's engines have flush-topped boilers, and only the newest have cabs, and are fitted with steam-brakes. They all have no dome or safetyvalve on the boiler, but a dome fitted with two safety-valves on the fire-box. The other bogie engines have 5ft. wheels and smaller boilers. The oldest batch of engines supplied to this railway are the only ones which have not bogies. They have 5ft. 6in. wheels, and are used for passenger traffic; but there is no great distinction between passenger and goods engines, all being coupled, and none having higher wheels than 5ft. 6in. If any further dimensions are required, I will endeavour to furnish them.-STRATHSPEY.

134139.]-Compressing Air.-A cylinder 3in. in diameter and lin. long contains 7:07 cubic inches. Tris number is contained 141'4 times in 1,000. The space occupied by a volume of air (providing the emperature remains the same) is inversely proportional to the pressure. In this case the original pressure is 1471b. per inch, and as the original volume of air is reduced it would require 141'4 times the pressure to compress it into this space.

T. E. J.

1414'

[34140.]-Limelight without Oxygen-For the lantern neither of the lights you mentioned is of any service for heating effects. Fletcher's appamatus is the best.-W. J. LANCASTER.

34140.]-Limelight without Oxygen.-I have both Fletcher's apparatus and a pyro-hydrogen lamp, and my opinion is that while the pyrohydrogen lamp gives a beautiful white light very uitable for any optical use or lighting purposes, the Fletcher apparatus is only to be compared with the Eight from a red-hot poker.-W. J. CHADWICK. (34145.]-Speculum Grinding. The meaning of wide swinging strokes" is that the upper glass must be rubbed round the edge of the lower glass, so that as the lower one remains steady the upper onedescribes a wide circle round it (see Fig. 1 of the paper referred to). The handle can easily be Cemented on by Kay's coaguline, price 6d., of any etemist. The best test for the curvature is that given in Volume X. by Mr. Purkiss, and again quoted in the last volume by "Ecnal," page 124, No. 681. Dr. Draper's paper is published in the fourteenth volume of the "Smithsonian Contributions," which volume being extremely massive and well printed, must be very expensive. Mr. Parkiss's instructions in Volume X. are capital, and I should advise" "Angleterre "to read them.-F. W, B.

[34149.-Induction Coil-The primary wire should have been thicker. Number 18 would have worked better than 20. The central core should The secondary coil seems good enough, and you have been in, diameter, filled with the iron wires should obtain a spark fully 1-6in. long, going up almost to fin. You have of course connected the condenser in the proper manner to the primary cannot from your query find any other points that built up right, and have tested for length of spark I suppose you have the secondary between the terminals of secondary, and not the primary, as stated in query. Let me know how you

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[34164.]-Inactivity of the Liver.-Try as much jogging about on a pony as your little boy can stand. Let him have coarse oatmeal porridge for breakfast, take plenty of milk, and live plainly.— ANTARES.

[34170.]-Mortgage.—If by taking the property Finem Respice means treating it as his own absolute property, then B cannot take the property without notice to A. He may, however, if he pleases, take proceedings for foreclosure in the Chancery Division of the High Court, or in a county court if the debt be under £500, and will then obtain a decree giving him the property absolutely if the debt be not paid within a time fixed by the court, or he may enter into possession of the property and receive the rents and profits and apply them in payment of his debt and interest. In the latter case he will be liable to render an account of his receipts and expenses. "Finem Respice" will find an answer to his next question in the mortgage deed, but if this be in ordinary form B may sell the property after giving six months' notice to A, or after some interest has been in arrears for three months, and such sale may be either by public auction or private contract. If B sell, and the interest, he may sue A for the difference upon the money produced be not sufficient to pay debt and covenant, to pay which is no doubt comprised in the mortgage. This action will be in either of the common law divisions, or in the county court.SPERANS, Lincoln's-inn.

K

[34171.]-Orthographical.-The words "ec and "ex," which are used as English prefixes, come from the Greek preposition, is, also before a vowel, -from, out of. The Latins changed the Greek into c, and the into ex, so that here is the key to all these ecs and exes: eccentric, out of the centre; export, to carry out of a country. A Greek-English word-root vocabulary, that any one can easily carry in the pocket, is a never-failing source of information and entertainment. The nonclassical reader would be really astonished at the very large number of English words whose parentage come from ancient Greece.-STYLUS.

The

[34175.]-New Forest.-You could not do better than making Lyndhurst your resting-place. Crown Hotel, opposite the church on the hill, is the best place to put up. If you come by rail you will have three miles to walk after you get out of the station, all on a straight road. You are then in the very heart of the forest. In the summer months a 'bus plies to and fro from the Crown Hotel to the station, so you can ride if you like (6d. is the charge). You will find what you require in the shape of quietude. I can assure you. You can make excursions to Rufus's Stone, Minstead, Bolderwood. Be. sure not to forget Holmsley (7 miles from hotel) where the huntsmen meet in winter, or else you will Brockenhurst, Boldre, lose a very grand sight. Lymington, Beaulieu, Ringwood, and if you have your bicycle with you, and do not mind roughing it, you can visit Christchurch, Bournemouth, and Poole. The roads to these places are a little better than the rest, only they are so very hilly-a continual up and down very nearly all the way. At the present time (September) pigs, &c., are in hundreds roaming about after the beech nuts, acorns, &c. ; but there is a very great scarcity of this kind of food this year. At other times of the year you will find hardly any cattle at all. Generally about the three first weeks in September, when the pigs are about, from the old sows down to the little pigs of about six weeks old are all over the place. In June and July and thereabouts you will find plenty of butterflies, &c. As regards the swamps, you will find it pretty free from them, unless you penetrate very far in places that recommend you to make friends with the keeper are not much frequented. However, you will find plenty of foot-paths to lead you about. I should belonging to that district, where he will be able to show you about. The road to Christchurch is straight, 14 miles from hotel, 7 from Holmsley station; Bournemouth, about 20 miles; Southmiles. There is one thing that I had nearly forampton, 11 miles from hotel; Ringwood about 12 gotten, and that is the tramps, where you will find

34146.]-Hall Marks.-1. The year in which the letter A was stamped-i.e., the commencement of the 20-lettered alphabet-does not coincide with the first year of each reign, but each assay office has alphabet, Also the alphabets have been continuous annual day appointed to change the style of since the date of their origin, with the exception of a few alterations. I will now state, to the best of my abilities, the annual day for changing for all the Onces:-The Goldsmiths Hall of London employ letters A to U inclusive (omitting J), forming a ycle of 20 years, the character of the alphabet being varied every succeeding cycle. These letters are changed on the 30th of May in every year, the office suspending business on the two days pre- have made connection both between primary and them occasionally about, and also the people that live

coding. Each letter is therefore used during the
Boieties of two calendar years. The Goldsmiths'
Company of Edinburgh change their character of
alphabet from Michaelmas to Michaelmas (29th
Sept.). In Scotland the custom has been to use the
letters alphabetically from A to Z, omitting J, thus
making a cycle of 25 years.
It is the same in
Dublin. 2. When one alphabet is got through the
Text is different, which holds good for all offices.
For instance:-(1) London, 1856-1876, Old English
Small: 1838-1856, Old English capitals. (2) Chester,
14-1884, Old English small; 1839-1864, Old English
Old English caps.
pa (3) Exeter, 1857-1877. Roman caps; 1837-1857,
(4) Newcastle, 1864-1888 (the
whole alphabet being used except J), Roman smalls;
19-1884, Roman caps. (5) Edinburgh, 1857-1882,
Egyptian capitals. (6) Dublin, 1846-1870, Roman

are at all wrong.

cells, and between primary and condenser-then I
may help you.-W. J. LANCASTER.

[34152.] Florentine Bronzing. Add one tablespoonful of hydrosulphuret of ammonia to one quart of water, then brush over the article to be bronzed.-ELECTRIC.

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[34162.]-Organ Music.-Hesse's "Organ Book," price 128. net, aud Julius André's first and second Organ Book," price 6s. each, published by Boosey and Co., 295, Regent-street, are charming collections of voluntaries in the true German style. The pedal obbligato is of moderate difficulty, and any awkward passages have the toeing and heeling marked. You will find some showy but interesting pieces, with very moderate pedal obbligato, in The Church Organist," by C. Collin, complete in 3 books for 8s. net, Novello

to offend. The pigs, in general, belong to them. I in the huts, regular squatters, and rather dangerous I might say that the forest is a lovely place in the summer; plenty of large trees. You say you wish to penetrate as far as the Southampton Water. Well, I must tell you you cannot do so altogether, because there is private property bordering in some places. You will be able to get to the water at the following places: Eling, and portion of Marchwood, near the magazines, Hythe and Eaglehurst. You can obtain a small map and guide-book for 2d. or 3d., which I have used for a very long time, and found it pretty correct. It is to be obtained of Heywood and Sons, Oldham-street, Manchester. It is called "Guide to Hampshire." The guide is of not much use, but the map is exceedingly cheap, and very useful.-TELESCOPE TELE.

UNANSWERED QUERIES.

The numbers and titles of queries which remain unanswered for five weeks are inserted in this list, and f still unanswered are repeated four weeks afterwards. We trust our readers will look over the list, and send what information they can for the benefit of their fellow-contributors.

Since our last "Amateur" has replied to 33079; "Jack of All Trades," 33264, 33281; ** Ohm," 33619; C. Detaille, 33659;" Ploni Almoni," 33722.

33463. The Lemon Cure, p. 482.
33466. Sizarships, T. C., Dublin, 482.
33467. Engine for Boat, 482.

33468. Purification of Manganese Chloride, 482.
33469. Distillation of Shale, 482.

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33756. Land Surveyors and the Colonies, p. 586. 33762. College of Surgeons, 586.

33770. Gatling Gun, 587.

33775. Medical, 587.

33783. Midland Railway, 587.

33786. Musical, 587.

33787. Lamp, 587.

33789. 8.8. Arabia, 587.

33797. Model Steam Launch, 587.

33799. Deformed Leg, 587.

33806. Flying Scotchman, 587.

33815. Chinese Screw, 587.

33816. Civil Service Appointments, 587.
33818. Legal, 587.

33824. Preserving Fruits, 587.
33826. Submarine Torpedo Boat, 587.

QUERIES.

[34194.]-Voltaic Electricity. I have a small Daniell's battery. Some time ago I found that after it had been working for two days the porous cell was covered on the outside by a thin crustation of a white powder. Can any of "ours" explain this P-SPERO MELIORA.

[34195.]-Curing and 8moking Herrings.-In looking over my back numbers I came across a good description as how to salt and cure the above. Could I make a small wash-house do for the smoking business, or will the pyroligneous acid accumulate on the walls, &c., making everything sticky P-COOK.

[34196.]-8.E.R. Locomotives.-Could any correspondent give particulars of 259-278 class of engines ?W. A. F.

[34197.]-Hydraulic Rams.-Would not a small water-wheel, and having a crank on each end of the arbour, each lifting a lever, and by its weight in falling acting on a pump similar to the feed-pump of an engine, be more economical than the ordinary ram, as the pump or plunger could be made the size found suitable and the lever weighted accordingly. This is only an idea of mine, as I do not exactly understand the rams, but I am thinking of using this principle to work a small waterengine. Kindly give me your opinion and oblige-L. W. DAY.

ma,

[34205.]-Dynamo-Electric Machines.-"Sigon page 541, Vol. XXVI., gives a very interesting article on the above, but to those unacquainted with electro-metallurgical operations the table he gives conveys no idea whatever of the strength of current. He would oblige, therefore, by telling us the number and kind of cells to do the same work as the smallest machine in his table, also the gauge of wire to produce the result he gives.-MODERN ATHENIAN.

[34206.]-Pressure Gauge for Model Boiler.I should feel obliged if any reader could inform me how to construct a gauge for vertical iron boiler 15in. x 9in. Also the greatest pressure I could safely put on a slidevalve cylinder, bore lin, and 2in. stroke. Also dimensions of spring or lever safety-valve to blow off at the required pressure. I have searched back to Vol. XX., but find nothing to suit my case.-THE MECHANICAL MASON. [34207.]-Madras.-Can any of your numerous readers give me any information as to the climate of Madras, with the cost of living, and what would be the most suitable clothing to take from England ? Any suggestions to a gentleman going out would be received

with thanks.-J. A. M.

[34208.]-Dynamo-Electric

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Machine.-Would Mr. Lancaster send the details for making a model machine, as he promised? I have carefully noted each number of "ours and have failed to notice them.-TYRO. [34209.]-Gas Burners--Would some of your numerous contributors kindly give me some information as to the most economical form of gas burner? I consume a considerable amount of gas, and think that my burners (fish tails) are very extravagant ones, but am puzzled to know which to adopt in exchange. Have any of your correspondents tried Cuthbert's burner? I should also like to know what quantity of gas an economical burner consumes per hour.-MANUFacturer. [34210. Tangye's Horizontal Engine ("High Pressure.")-Could any kind reader favour me with a rough sketch, also full particulars how to make one? The cylinder about fin. bore, lin. stroke.-YELLOW WITCH.

[34211.]-"Boiler Portable Multitubular."I am about making a "boiler," but should like a little information about the pressure, also thickness of plates, size of fire-box and water space? I intend making it about 14in. long, 4in. dia. It is a loco-type I require in iron, and how many brass tubes should require? Any kind reader giving me a sketch, I shall be greatly obliged. Pressure about 601b.-YELLOW WITCH.

[34212.]-Pumping Water.-Will some kind reader show me the simplest method to obtain the length of each pumping set, which is worked by two quadrants, in order to dispense with counter balance weight, so that the engine or sets be equally balanced? Particulars as follows:-Two pumping sets, each bucket being 16in. dia.; depth to pump, 80 fathoms; weight of 80 fathoms of lowset spears, bucket, plates, &c., 17,7001b.; weight of 40

B

fathoms of high-set spears, bucket, plates, &c., 9,3501b.; average weight of 1 fathom spears, 2021b. (spears, plate, bolts, taken only). Pumping arrangement is shown in sketch:-A, connecting rod; B, connecting rod to engine; C, low-set spears; D, high-set spears. Centres of quad. rants equal distances. If my calculation be right I make the high-set 46 7 fathoms, and the low-set 33-3-for each to balance.-J. M. G., Ferry Hill.

[34198.]-Hydrogen Gas.-Will any reader inform us how to make hydrogen gas out of steam of water, and the apparatus and materials used in making it ?-P. C. D. [34199.]-Fire-Arms.-Will any reader inform us how to cut the chequer work of a gun-stock and tools [34213.]-Printing Machines.-I am about making used, and how to stain and polish a walnut wood-stock? a printing machine to work from a No. 2 horizontal Also how to give a good blue-black to a rifle barrel.-engine, pressure 45lb. per square inch. I want it to ink C. P. D. the type itself. Any kind reader giving me full size and a sketch will oblige-YELLOW WITCH.

[84200.]-Deafness.-I am employed on board a light vessel where the fog-horn is blown by steam, often many hours together, and find the strong noise is causing me to be very deaf, even for days after, and I fear the entire loss of the sense of hearing. Can any of your readers kindly suggest any means I could adopt to prevent the loss I fear, and the fearful inconvenience arising from the use of the fog-horn ?-JOHN F. WARDER.

[34201.-Lunar Temperature.-I shall be much obliged if any correspondent would kindly inform me as to what is the cause of the moon's temperature varying from one extreme to the other, seeing she has no atmosphere. It is estimated that the temperature of space is 224° below Zero of Fahr. thermometer.-G. W. B.

[34202.-Soldering Imitation Stones to Metal.-Can any of your readers give me the compo. sition that jewellers use to solder the imitation stones to metal, &c.? I believe the Birmingham jewellers use a great deal of it. It is not a cement.-A CONSTANT HEADER.

[34203.]-Legal Question.-By his will A apportions his property to his grandchildren, his wife, and daughter (mother of the grandchildren) having a life interest in it. Should any of the grandchildren die before the age of 21 years their shares to be divided among the surviving grandchildren. The testator's daughter dies, then two of the grandchildren, both over 21 years of age, unmarried, and without making a will. Does the father of the deceased grandchildren heir their portions on the decease of testator's wife? If not, who does? Or are their portions to be divided among the surviving grandchildren ?-EQUITY.

[34204.]-The Bigns of the Zodiac.-Can any correspondent say to whom we are indebted for the origin of the Signs of the Zodine, whether or not they bear any signification, and, if so, what that signification is ?-H. B.

FOLTON.

[34214.]-Ellipse.-Will any one describe an instru. ment which will describe a true ellipsis or oval, from one centre, with as much facility as a circle can be made with a pair of compasses ?-W. M.

[34215.]-Stained Marble.-The upper slab of a white marble mantel-piece has a large brown stain on it, which spreads gradually from the back towards the edge. I fear that it must be caused by smoke passing through some crack in the brick-work. Can any of ours" tell me how this stain can be removed, and if it can be done without displacing the marble, which would involve repapering the room?—OTTER.

add that I have access to Hogg, Beale, and Carpenter, on the microscope, also the "Micro-Dictionary."-WALTHANsrow, Port Natal, S. Africa.

[34219.]-Compressed Paper.-Could any corre spondent give me information concerning this? Wanted to know how it is made from the pulp, pressure required, and its useful purposes.-PAPIER MACHE.

[34220.]-Oval Vessel.-Will some brother reader kindly answer me the following query? An oval vessel made of wood, in the same manner as an ordinary tub is, about 20ft. high, its major diam. exceeding its minor by about one foot. The vessel when finished was filled with water, but when about two-thirds full, the upper part, which was open, took the form of a circle, but returned to its original form when emptied. Please explain the reason.-F. J. O. C.

[34221.]-Coca and Potassium.-Will "Incag" please give me directions how to combine coca and potassium, as recommended by you for heart affections, &c. P I am out-doors most of my time, and when overfatigued I often feel a sort of cramp over the heart, especially during cold wet weather. You recommended the chlorate of potash for my hay fever; I should like to try the coca in addition, if you approve of my so doing.F. W. S.

[34222.] Blast Furnace Slags.-To Husn CLEMENTS.-How do you determine the duty of alumina in a slag, as to whether it acts as a base or an acid, as I believe both duties are attributed to it in some instances? Can you give me the analysis of an average slag made in the Lincolnshire district; also one of Northamptonshire ores ?-F. W. S.

[34223.]-Preventing Varnish and Zinc White from solidifying.-Will some reader inform me how I can prevent a mixture of spirit varnish and zinc white from solidifying? It seems to form a kind of soap, and I have tried a number of different gums-some dissolved in alcohol, and some in spirits of turpentine-but the result has been always the same. Cannot something be used to keep the mixture fluid ?-AMERICUS.

[34224.1-Chemical.-Would it be practicable to recover tartaric acid from sodic tartrate by the use of sulphuric acid? The sodic tartrate is formed in a gasegene by the action of tartaric acid and sodic carbonate in solution, and I propose adding sulphuric acid, crystal. lising and then washing away the sodic sulphate. What I want to know is if the H,SO, would change the compo sition of the tartaric acid P-H. R. M.

[31225.]-Lens.-I have an uncemented astronomie object-glass of 34in. aperture; it seems rather a good glass, but appears never to have been cemented; a few drops of water pressed between the glasses increases the clearness of the combination, and, I think, adds slightly to its definition. I wish to know if 3 objectives are usually sold uncemented, and if it would improve mine to fix the concave and convex together with balsam CASSIOPEIA.

[34226.] - Refiguring.-Have any of my brotherreaders got their object-glasses refigured ? Is it a difficult or an expensive alteration; and inferior objectives are. I opine, defective rather in their curves than in the quality of the crystal ?-CASSIOPEIA.

[34227.]-Monochord.-Can any of your correspondents inform me how to make a monochord, accurately divided, such as that illustrated in Tyndall's "Lectures on Sound," p. 86, or say if such instruments are sold?MUSICUS.

[34228.]-Ammonia.-Is it possible to obtain hydrosulphuret of ammonia without the offensive smell? Could I use any means to deodorise it ?-HYDROGEN.

[34229.]-Weather-glass. For some years past there has been in my possession a weather-glass-at least I've been told to call it by that name. It is a cylindrical with a brass cap, with a hole in it, by which the instru glass vessel 10in. long, and about lin, in diameter, covered ment is suspended. The vessel is about three-fourths full of a clear amber-coloured liquor, and the bottom is about one-fourth covered (in the liquor) with clear crystalline grains of a white colour. I have seen smaller tubes filled with a liquor of a similar colour attached to Fitzroy weather-glasses, but never could find any one who could tell me their use. Would some one let me know what signs the instrument shows to indicate approaching changes P-AEROLOGIST.

[34230.1-Law.-Will some correspondent inform me whether or not a Cambridge local certificate (2 languages) will fill the place of a preliminary law certificate P-BLUE

BAG.

[34231.1-Oxygen from Chlorate of Potash.Will some chemist kindly say if it is possible under any conditions for oxygen to be evolved from chlorate of potash in solution, in the presence of an alkali P-R. M.

[34232.]-Husband's Liabilities.-Will one of our legal friends please describe the course of the law in the following very simple case:-A, a husband, borrows money on promissory note, and also procures goods on credit from X. While thus in debt A dies. B, the wife of A, augments the account by getting further goods from X. B marries another husband, C. C, well knowing the state of the account, and also the over-kind nature of X, procures still more goods on credit. Now X, supposing that B must be responsible for her dead husband's debt, and C must be responsible for B's debts, sends the bill for the lot to C. C coolly repudiates all responsibility beyond the amount he himself got after his marriage. What is the law ?—TIM BOBBIN.

[34216.]-Concertina.-In pulling ont my concertina the fifth note of the left-hand side plays all right, but in pressing it back again the note will not play, and sounds as if there was not room for the air to escape. Can any kind reader inform me how to repair it ? I have taken it to pieces, but find no stoppags.-S. GREENSLADE. [34217.)-Magneto-Electric Machine.-I have recently constructed a machine on Clarke's principle, but cannot obtain any sensible current from it. Coils wound [34233.)-Railway Bridges.-Which is the largest with lb. No. 18 wire; soft iron cores 24in. long, fin. dia- railway bridge in the world, and what is the length of it? meter; horse-shoe magnet 104in. long, made of steel 1in.-A CONSTANT SUBSCRIBER. wide, ifin. between poles. The spindle is insulated from one support with ivory. The commutator is made accord- [34234.]-Boiler for Steam Carriage.-I intend to ing to the descriptions in the books, so far as I can under- build a steam carriage to hold four persons, and I a stand them. Number of revolutions, 1,000 per minute. going to drive it with a pair of 3in. cylinders. 1 hou Cannot find a current in the coils. Can any of ours like very much to know what would be the best design of suggest a reason for the machine not working, and give boiler to construct, and also the dimensions. Would Mr. me full instructions for making a commutator P-K. C. L. Nicholls, or any other practical correspondent, answer

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this ?-ALEXANDER. [34235.] - Relation between Power and Weight-Will some correspondent inform me how to arrive at the relation between power and weight when applied with worm and worm-wheel? The books that I have consulted vary considerably.-R. H. T.

[4236.]-Filberts.-Can any of our correspondents give me any information about the cultivation of filberts on rather a large scale?-R. P. S.

134237.]-O.G.-I bought an O.G. for nearly £5. It is of 3 aperture. Having fixed a page of the answers of this paper on an opposite wall exactly 50 yards distant, I was surprised to find it all but impossible to read it with any of the eyepieces supplied with the telescope, which altogether cost over £12. I have plenty of power, bat the letters appear confused and misty, or run together into dark lines. The larger print, such as the name on top of page, ENGLISH MECHANIC, is sharp and well-defined. No coaxing with stops that I have tried improves the definition on small print. I wish to know at what distance a first-class objective of this aperture, 3in., will define the print in answers column, and what is the matter with mine.-SHEFFIELD.

boys have to be taught, and drums will be added later on, when some proficiency has been attained in playing the flutes.-C. LARK.

[34250.]-Liquidation.-A is mortgagee of a terrace of leasehold houses. B, the mortgagor, liquidates. A trustee was appointed; there being no estate the matter has lain dead for some time past. C buys the leaseholds, and has paid off the mortgage; the amount of the purchase money paid by C to A is said to have exceeded the amount named in A's security. A most likely lent money to B after the mortgage security was given to him. but before B became bankrupt. If so, ought he not to have proved his debt in the usual way as an unsecured creditor, and can he not be made to pay over to the trustee whatever moneys he may have received in excess of his security? Supposing the trustee, who is a small tradesman, to have been induced to sign necessary papers at the request of the solicitor to the liquidation without having had the matter correctly or sufficiently explained to him, can the matter be re-opened by the creditors? If so, would it be expensive ?.-Q.

[34251.]-Geological Time.-Can any geological correspondent give me in round numbers the time that has elapsed between the drift period and the present time; and has it been proved beyond reasonable doubt that man existed at that period? Also, was the Manderthal skull found below the strata formed during the glacial period?

[34238.1-Mining Questions.-1. A pit has been sunk through a series of flat strata to where it has cut beary feeders of water. How is a dam to be contrived and put in to keep the water from getting up the shaft into shallower workings ? 2. Discuss the subject of spragging and propping in a seam of coal of moderate strength, worked by long wall, and how it is possible to adopt a certain measured interval between such props. 3. Describe the mode of timbering wide gunnies or vein xcavations, where the lode is upwards of 18ft. in width. 4. Enumerate the different classes of rock found favour--SANKORRA. able in various regions as country of the lodes. 5. Having to transmit for half a mile the power for pumping, describe the rods used for the purpose and the means of breaking the angles in their course.-COLLIER.

[34239.1-Organ Building.-May I trespass so far on your kindness as to ask room for a few questions respecting a small organ which I desire to build in my own house? Not having much spare cash at command I am wishful to secure the advice of some of your kind and very able contributors as to how my money may be best pent, and also as to what stops they would recommend for an organ of the dimensions given below. I should also feel grateful if they would say how much I ought to be called upon to pay for such an organ if plainly built without useless ornament. The organ is intended for a room of considerable length and breadth, about 8 yards by 4 yards, and about 12 feet high. It should have two manuals with, say, three stops in each, and room for a spare stop when I can afford it, and a set of bourdon pedals-independent, of course.-KAPPA.

[34240.]-Orange Bitters.-Can any reader give me good practical receipt for making these bitters? I understand they are a capital tonic for the stomach.DTSTEPSIA.

32411-Varnishing Wood.-What is the best way to fill up the pores of wood preparatory to varnishing with oil varnish, so that the work when finished looks as if it were polished, the beauty of the grain being preerved? I have tried sizing, but the work won't stand rabbing down with pumice and water between the coats of varnish, and to fill up with varnish only takes a very long time.-DANDIE DINMONT.

(34242]-Lightning Conductor.-A friend of mice in the country has a large oak just in front of his house. Can any one tell me of a cheap and simple conactor for it (the tree), and about the point at top, how to connect it to earth, and how to fasten it up, with approximate cost of materials ?-H. W. W.

[34252.]-The Collision of the Princess Alice and Bywell Castle.-Have any of the unfortunate survivors, or the families or representatives of deceased parties who lost their lives through the collision, any claim for loss, damage, &c., against the proprietors, &c., of either of the two vessels? It appears by the newspapers it is probable the proprietors of the Princess Alice may take proceedings for £25,000 against the proprietors of the Bywell Castle.-A COLLIER.

[34253.]-Painting Baths.-I have two tin baths fetches it off, and I now find rust is taking the bottoms of which I have done over with white lead, but the hot water them, and they will soon be useless. Would "Bark Tom" kindly say if those paints he recommends in 33139, p. 505, clean old paint off, and how ?-J. W. P. last vol., will stand the hot-water test? Also, if I should

[34251]-Pattern Making.-I should feel very much obliged to any reader who will kindly recommend me a good and cheap work on engineers' and builders' pattern making ?-EMBRYO ENGINEER.

[34255.1-Converting Telescope.-Will Mr. Lancaster inform me how I can alter an astronomical telescope of nearly two inches diameter into a terrestrial, or. in other words, how can I alter the eyepiece so as to give desired result? The telescope is one of Dollond's, and an erect image? Would an additional lens give the the eyepiece consists of two parts-viz., an eyelens and object lens.-E. J. MARKHAM,

[34256.]-Velocity of Pulleys and Shafting Revolutions.-Would some one kindly solve the following for me? An engine shaft makes 120 revolutions per minute, on which is a 3ft. driving-wheel, driving by strap a 2ft. 6in. diameter pulley, and on the same shaft is a 4ft. diameter pulley driving by strap a pulley 1lin. diameter, on which is a 4ft. saw. What is the velocity of the saw and the revolutions of the saw-spindle? Perhaps some one would give a simple formula for working

this out?-ONE IN A FOG.

66

[34243.]-Blackening Tools.-Can any one tell me how to blacken such tools as engineers' shifting wrenches [34257.1-Busty Pump.-Will any of your readers which have got rusty? I have no forge.-H. W. W. be good enough to tell me how to get rid of rust in a pump? It is W. and B. Douglass's, patented 1842. The 342443-S. E. R. Engines.-Can any reader give me particulars of the following tank engines:-Nos. 13, 206, through the pump it is hardly fit for use, especially water in the well is perfectly clear, but after passing or 213 old Greenwich engines; Nos. 73 or 143 new Green-washing linen. I did not notice any appearance of rust wich and Woolwich engines, with cabs; the trailing bogies, for two years after it was fixed ?-RUSTY PUMP. No. 210; the shunting engines, as No. 75 (I am not quite sure of these last two numbers); and the flush[34258.]-Repairing a Vice.-I was very glad to see topped tender engines without dome (single and coupled). Chelt's answer to this, explaining how to put in a G. L. P. sure that the Brighton "Terrier" at Paris double thread, which I am sure is the best, and don't a saddle-tank? All that I have seen have wing- see much difficulty about it except in the brazing, which tanks.-H. W. W. is a thing in itself I am sorry to say I know noth ng (34245.]-Dance Music.-In a set of "La cers" how about, and therefore would be greatly obliged to "Chelt many bars go to each figure? What I mean is-supposing full-planation of Low to braze, not only the vice nut (or any other reader) if he would give me a simple and ach figure to be danced in perfect time, how many bars would have actually been played by the time the figure work Have a vice, but it is no use, as the thread is gone. (wa h is most particular), but also for all ordinary was completed ?-Õ. A. E.

34246.]-Gas-pipe as Return Wire.-I am working out a system of electric gas-lighting for public lamps. Can I use the gas-main and lamp-pipe from just below the burner as return, or must I lay out a return wire? I have no doubt the gas-main would serve, but am doubtful whether the connection of lamp-pipe to gasmain is to be trusted.-EXPERIMENTALIST. 34247.]-Optical Illusion.-I have frequently noticed, in passing through railway tunnels by night hen the light of the carriage renders the masonry reable, that after looking steadfastly for some time, it impossible from mere observation to distinguish which ay the train is advancing, the brickwork sometimes appearing to fly past in one direction and sometimes in the opposite. I have thus often been puzzled-on waking from a nap, and having forgotten which side of the carriage I had taken on entering-to know which was the front and which the back of the train. Can any one explain this? I ask this more particularly because iz lightning, seems to be of opinion that it is improbable zieht in his reply (14844), on the question of ascendthat the eye should be deceived in judging the direction

L

of motion.-C. A. E.

[34248.1-Flutes in D.-Will some one of our instrumentalists kindly inform us as to the reason why a date should be set in D or B flat rather than in C? I presume there is a reason, although on first thought it would seem preferable to have flutes set in C, so that the bator sharps required for play in any other key would be the same as on pianoforte, violin, &c., instead of aving to make some natural that have already been dattened or sharpened, as the case may be. Brass instruats too, I believe, are set in such keys as B flat and E fat; so perhaps the same reason will apply to them.-C.

LARK

3429]-Fife Band.-Will some of "ours" give me bint or two on the formation of a £fe band for boys? Wat key should the fifes or Autes be in-D, B flat, or FP Will the same-keyed fate do for a first or second part ? If not, which should take first and whisk second? The

-J. P.

men me a good book on British fossils P-A CORNISH [3259.]-British Fossils.-Can any reader recomORGANIST.

[34260.]-Reflecting Galvanometer.-I wish to make a reflecting galvanometer and should be obliged to any correspondent who would kindly inform me how to make an inexpensive one.-W. B. D.

ELISH MECHANIC, I have made a telescope, with a 2in. [34261.1-Microscope.-With the assistance of the object-glass and two astro. eyepieces, power of 70 and 185, and day eyepiece 36. Now I want to make a microscope out of the same lenses. Will some of our friends tell me which of the above lenses will work the best, and how to place them for distance ?-ENGINEER.

[34262.]-Marine Engineering.-My son is desirous of going to sea as a mariue engineer. He has had a very fair education, and is 16 years old. He has been for two years in a civil engineer's office, and is a very fair sea. draughtsman. He is very fond of machinery and the I believe the Board of Trade require candidates to have been four years at sea or four years in a marine engine shop and one year at sea. Could any one tell me which would be best for him to go to, and where to apply, as I do not want him to remain in it all his life ?-PRES

TONIAN.

[34263.]-Folding Screen.-Being about to make one of these, I would be glad of information as to the usual height and breadth of the frames (of which I pure rose to have three), and the dimensions of the timber? Does the frame require any diagonal tie ? What kind of hinges are used? Also what kind of material is to be tacked on for the ground, to paste the pictures on? In short, any wrinkles will be appreciated by-A., Liverpool. [34264.]-Pumps (Universelle Steam.)-I wish to make a pump, similar to Hayward Tyler's make, and with size of pump, &c., &c. Lonly want to me all should be obliged if any reader could give me a sketch, pump, say cylinder qiu, bore, pressure from boiler 5010. YELLOW WITCH.

[34265.]-Composition of Storm Pedal.-In turning over a book on the organ, I came across a "storm pedal." Can any reader give me its construction ? and oblige-C. T. S.

[34266.]-Dirt and Oil.-I have at times a considerable quantity of a liquid containing water, soap, oil, and dirt, the products of a waste-cleaning process. Could some chemical or other correspondent inform me of the best method of extracting the dirt, and making the rest useful? Could it be made into soft soap, and how ?— CLEANER.

corrosive.-Having occasionally to make a few small [34267.]-Plating Wrought Iron with a Nonmetal patterns of wrought iron to cast from, I should be obliged if a practical reader would give information how to coat said patterns with a non-corrosive metal with a solution, so as to leave sand well, and not to corrode with use. If a battery is necessary, will "Acidum Aceticum " say what his porous pot is made of, and if the sheet of copper must be soldered to form a cylinder, or simply bent to shape P-MECHANIC.

practical person kindly advise me what to do with my [34268.]-Crooked Lathe Mandrel.-Will some lathe? The mandrel appears to me to be crooked, as another. It makes a loud shaking noise, except just fresh after making a box the lid fits better one way than oiled, or in turning wood supported at both ends. The bearings are not evenly worn, and the smith tells me it is because it is not worn enough; but it has been in use a year or more; sometimes the mandrel sticks fast in the bearings after working a time.-A DORSET AMATEUR.

[34269.1-Precipitating Iron out of 8olution of sulphate of Soda.-Will some correspondent inform me the best method of precipitating all the iron out of a solution of sulphate of soda, so as to make nice white crystals ? I dissolve about 35 cwt. at a time of saltcake, which makes about 1,700 gallons of brown liquor. brown with iron. Lime will make the liquor white, but it does not cause all the iron to fall out.-H. HOYLE.

USEFUL AND SCIENTIFIC NOTES.

M. VAN DEN BRANDEN, the archivist of the town of Antwerp, has published in the Précurseur an original bill of sale of the 1st of September, 1547, for twenty-two bottles of petroleum. This shows that at that date petroleum was already imported into Antwerp.

Improved Process of Vulcanisation.-On p. 6 we gave a description of a process of vulcanisation, patented by Mr. W. Abbott, which consists in subjecting the articles to be vulcanised to the vapour of sulphur chloride, subsequently nentralising the effects of acid by dipping them in alkali or exposing them to the fumes of ammonia. Mr. Thomas Forster has forwarded us a specification, dated October 10, 1876, in which he explains how he uses a mixture of chloride of sulphur and bisulphide of carbon to valcanise rubber goods, and subsequently exposes them to the vapour of ammonia. It would thus appear that Mr. Forster's patent anticipated Mr. Abbott's, so far as the use of chloride of sulphur is concerned.

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Florence, of the Howgate Arctic Expedition, CapThe Howgate Expedition. The schooner tain Tyson, has, it is believed, already left the northern waters, and is now on her way home. Captain Roach, of the wrecked whaling schooner Helen F., for which the Florence on her ontward-bound trip one year ago carried supplies, has arrived in New Captain Tyson (July 15), August 15 had been fixed London, and reports that when he parted with Some months ago Captain Tyson induced twelve upon as the day for the departure of the Florence. natives to join his crew, and secured a number of of the fur-bearing and other animals of the country dogs for use in future explorations. Many specimens have been collected.

A Double Expedition to the North Pole.From a communication recently received at the Navy Department, it appears that Mr. James Gorthe North Pole, one vessel going by way of Behdon Bennett contemplates a double expedition to ring's Straits, and the other by way of Spitzbergen. He has been in consultation with Petermann, the great German geographer, and other Arctic experts abroad, and now proposes to fit his well-known yacht, the Dauntless. for an additional Arctic expedition, putting in her an auxiliary engine and screw, and otherwise making her complete for an expedition by way of Spitzbergen. The Jeannette is on her way to San Francisco, and will pass through Bebring's Straits early next year. Her owner will spend not less than 120,000 dels. on the Jeannette expedition. He wishes the Navy Department to furnish for the Dauntless the crew, officers, and provisions necessary for her voyage, he making her otherwise ready. He is persuaded that the two vessels going in different directions, but by the two ways which are admitted to be the best, and the only ones which promise early suc cess, can more than double the chances of reaching the Pole. partment is, in brief, an inquiry to ascertain if His communication to the Navy Dethis proposition would have the favour of Secretary with the engines and screw with which Mr. Bennett Thompson. The Dauntless is a staunch vessel, and proposes to fit her, at his own expense, would be an excellent craft for an Arctic voyage.

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