REFLECTING TELESCOPES.-TO "Robinson Crusoe."

[14871.]-DON'T alter your telescope if its performance is anything like satisfactory. What you would, perhaps, gain in one way you would more than lose in another.

It is true the small reflector in the Gregorian will, when movable on its axis, enlarge the primary image almost to any extent, but it magnifies the imperfections as well. What it gains in power it leses in brilliancy-the image becoming dull and indistinct as it increases in size. Converting it into a Cassegrainian would about double its present focal length without increasing the length of body, and conse quently produce a larger image; but the spherical aberration would still be equal at least to a single mirror having primarily a focal length equal to such an arrangement. The small convex speculum can never correct the aberration of the large mirror so long as spherical curves are employed; besides the arrangements both of Cassegrain and Gregorian involve a considerable loss of light as compared with Newtonian.

Edmund.

NEWTONIAN AND GREGORIAN
REFLECTORS.

To "Robinson Crusoe."

[14872.-I HAVE read with very great interest indeed your letter (14783) on the above subject, and I earnestly trust you will, at an early opportunity (for the sake of a large class of poor amateurs, of whom I am one), make known the construction of the instrument in detail, and by what means you were enabled to arrive at such a satisfactory result at so very little expense. Ophiucus.

UNFERMENTED BREAD.

[14873.-J. F. E." (letter 14797) has put the unfermented bread process in a simple form, which any intelligent person will be able to follow. His formula leaves, however, a little free carbonate of soda in the bread. Instead of 12, I should put 13 fluid drachms of pure hydrochloric acid into the 10 fluid ounces of water; and, so doing, should still leave a minute excess of alkali in the mixture, according to my observation of the saturating power of the acid supplied to me for a series of years.

A Physician.

L. AND N.W. LOCOMOTIVE ENGINE-SHEDS.The Precedent (see letter 14796, p. 655) is stationed at Crewe, and she is a Webb's 6ft. 9in, coupled, not

5ft. 6in.-TAMERLANE.

REPLIES TO QUERIES.

• In their answers, Correspondents are respectfully requested to mention, in each instance, the title and number of the query asked.

[33030.]-Nitrate of Copper (U.Q.).-Your correspondent, "R. N. C.," bas rather an awkward material to deal with. I think his cheapest way would be to add fresh burnt lime in excess to the liquid, and if possible heat it. The copper will be entirely precipitated by this method, particularly if the whole mixture can be boiled, and the clear liquid above can be siphoned off and allowed to go wanted, but not very expensive to put up, and the to waste. Of course, some extra plant would be precipitated copper, which will be very impure probably, will more than repay the cost. The coppery precipitate might be dried as far as convenient, and offered to some copper-smelting firm to work up with other stuff. However, the question of profit or loss entirely depends on the amount of copper present: a very little probably would not be worth the expense of extracting.-AUGUSTUS.

24

7 guineas, and no one who can afford to give this
should think of a cheaper-made flute new. Yet
there are 8-keyed flutes, mostly well worth the
Finally, there are the pawnbrokers and second-bande-
money, to be had from two to four guineas new.
dealers generally, where a 15 guinea flute may some
times be had for 4, or a 30-guinea for 10. But there
is no guarantee of the instrument, and it should be d
thoroughly well tried throughout the scale, and care.
fully examined for concealed cracks, loose keys, &c.
in fact it would only be safe to buy on the advice
of a practical player. I may say something as to t
the material of which flutes are made some other
time in further answer to Mr. Colling's question,
meantime I trust he will find some help to guide his
choice, if not quite as satisfactory as I could wish,
in what I have already written.-BEROB.

(U.Q.).-As no one has answered this query I will
[33303.]-Isle of Wight Failway Engines
try and give "Murano "a general idea of the out-
ward appearance of these engines, taken from per
sonal observation about three weeks ago, but I don't
know any dimensions. Tank engines only are used
on the island. Those on the Ryde and Ventnor line
have inside cylinders, and coupled driving and
trailing wheels, and are painted brown, like the L.
and S. W. R. The cab is quite roofed in. They are
named after the stations on the line, and were built
by Beyer, Peacock, and Co., at dates varying from
about 1864 to 1876. On the plate of Brading I
Beyer, Peacock, and Co., Gorton Foundry, Man-
chester, makers and owners, 1876. The only engine
that I saw on the Newport and Sandown branch is
called Newport, and is painted like the others, but
has a single driving wheel, and was built by Juo.
Hawthorn, Newcastle. On the Ryde, Newport, and
Cowes line there seem to be different sorts-some
green, some brown. The only one that I noticed st
all closely was No. 2, Precursor, with single driving
wheel, and no cab. She was built by Slaughter,
Grüning, and Co.-W. E. H.

[33552.]-Steam in Small Boats (U.Q.).—I find that this subject, in which I am much interested, and in which also I have bad some little experience, has got under the U. Q.'s" column. I offer the following remarks in the hope that they will be of service to "Aquarius." The only advantage of pad. dles in small boats is that they can be propelled in very shallow rivers where a scrow could not be used, on account of the depth of immersion. In most rivers, where small boats can be used, there is gene rally sufficient depth for a screw launch, and in this case a screw is by far the best. Screw engines take up much less room than paddle engines, are quite as easy to keep in repair, whilst for removal at any time they offer better advantages, there being no paddles and boxes to remove, the propeller being easily taken off by beaching the boat. The prime cost is also in favour of screw engines, whilst cost of maintenance is less. I shall be happy to give any further information on this subject.-LANCASHIRE FITTER.

ค

[33234.]-Flute.-This query may deserve, even as late as this, more of an answer than it seems to have got. In direct reply to Mr. Colling's question let me say that the fingering of the Siccama flute does not differ appreciably from that of the ordinary eight-keyed flute, while the Boehm does very considerably, as does also Carte's special improvement of the Boehm. It must be remembered, however, that Carte as a manufacturer makes both a Siccama and a Boehm, and also that Boosey and others do, while each maker has also some speciality of his own as an improvement upon either the Siccams or the Boehm, or upon the ordinary flute. There are two considerations, however, that may decide or at least limit one's choice-first, how much one is prepared to give for a flate, and second, how "tolerably proficient" he has become with the usual fingering: had better not trust to smelting copper ores by a [33350.J-Copper Smelting (U.Q.).-"Frank" Flutes range all the way up to 30 guineas, and system on paper, as reactions occur in the furnace nothing satisfactory can be got new for less than which materially affect the result; but if he desires seven. Of course there are opportunities at second-to work in that way he had better make an analysis hand, but these are chances, not makers' prices. of an ore furnace slag that suits him for fusibility Now I do not know of any English-made Boehm to be and freedom from copper, and arrange his mixture got from less than 20 guineas, and that is about the of ores, also analysed, to coincide with what he finds.d lowest price of the French cylinder Boehms, though But surely he doesn't mean to work such an ore & a conical French Boehm can be got at about 12. the one he gives, so as to yield a slag containing Therefore, unless one is disposed to give about 20 guineas it is needless to think of the Boehm or its per cent. copper-it ought to contain not more than varieties. If. then, he is ready to spend this sum, it percentage of copper is. The ore might be unwork 4 per cent. at the utmost. He omits to say what the is worth while to consider his present degree of pro-able except as a flux to other ores, and I think that ficiency, and perhaps how much more he aims to would be the best purpose he could put it to.accomplish, before adopting the Boehm. I may say AUGUSTUS. in passing if he has practised on a flate with less than eight keys the sooner he changes the better, and he cannot possibly lose by change to any eight-keyed flute I ever saw or heard of. It is the greatest folly to begin on a flute with less-worse, if possible, than beginning the piano on a worn-out discordant instrument, for he will have to unlearn, in some degree, almost everything he teaches his fingers, if not his ears and lips, and the fingers are the slowest to learn of all. If, now, he has spent much time over and acquired very great facility on the ordinary flute, it may be doubtful whether it be worth while to go over all his practice again on a Boehm. It requires no slight determination and perseverance to overcome the discouragement of beginning anew, while through impatience one is liable to acquire other faults. I have myself changed from the ordinary flute to Carte's improved Boehm patent of '67, and I know how hard it is to unlearn and begin where one has made some progress and feels only like keeping on and making more. A friend has a 14-koyed Siccama on which he has gained such facility with many years of practice that I could not advise him to change, for it must be borne in mind that it is only "facility of fingering" that these new flute, as Pratten's, may have just as perfect a scale instruments offer. An equisonant Siccama, or other and as fine a tone as any Boehm. Therefore, unless one has a good deal of determination, and fully appreciates that he will have to unlearn much that he considers himself to have learnt, and is content to do so, I can hardly advise a change to the Boehm or its improvements. Consider, however, if one is young, that there is an immense facility gained for Silk-growing in Australia.-That silk-growing the execution of difficult music, and therefore, if will some day become one of the great industries of that class of music is in view, and it is intended to Australia seems to be net only a reasonable proba do all that can be done on the flate, it is worth while bility, but as near to an absolute certainty as any to begin again after some years of practice on the human expectation can well be. Over large areas, older system. For simple airs and music only I do the climate and the soil are singularly suitable, and not think the gain worth the labour of the change, silk is one of those commodities with which the since, as I have already said, there is hardly any world is never likely to be oversupplied. The demand improvement in the scale and none whatever in the for it is only limited by the price, and if increased tone over some flutes that are made for the older production can diminish the price, and still leave a fingering. Now, with 30 guineas to spend and the profit to the producers, there will be no difficulty Boehm decided upon, I would say choose Carte's about the consumption. The difficulties incident to improved pattern by all means. If, however, what I all new enterprises, and the slow process of experi- making the change, with the same money to spend have mentioned suggests good reasons for not mentalising under new conditions, combined with the greater temptations to rural industry in other direc-it would be well to compare for oneself Pratten's tions, have hitherto retarded the few efforts that have been made to develop an industry which will one day be seen to be natural to the country. It is satisfactory, therefore, to find that enthusiasm on the subject is not altogether non-existent, and that efforts are still being made to draw towards this industry the attention that it deserves.

Gas Cloth-"Gastuch," or gas cloth, is a name given by Dr. Hirzel, of Leipsic, to a gas and watertight stuff which he has recently patented. This is produced by placing a large smooth piece of socalled guttapercha paper between two pieces of some not too coarse and dense material-e.g., shirting (undressed) and then passing the arrangement between heated rollers. The outer pieces of the shirting combine in the most intimate way with the inclosed guttapercha to form a material which is impenetrable by gas and water. It may be made still denser and more resistant by being coated on both sides with copal lac, for instance. The material is said to be well adapted to form gas-tight membranes for regulators of pressure, of compressed gas bags, or sacks for dry gas meters, as also dry gas reservoirs.

model, made by Carte. I believe these the two most
perfected cylinder, made by Boosey, and Radcliff's
perfect flutes based on the old system. Those who
would give 10 or 15 guineas will find at these
makers and others various flutes with 10 to 14 keys,
and mostly of the Siccama model, or some modifica
tion of it, though they may not be called so always.
With German-silver keys these may be had as low as

[33570.]-Leamington Kitchen Range.-Con sidering the thousands of tons of coal that must be wasted every year on the ovens of these inefficient treated with so much apathy. "L." comes forward ranges it is a matter of surprise that the subject is as an advocate in their favour, but, after all, his evidence is of a very negative character. It does not appear that he has ever made trials and comparisons with some of the very economical portable cooking stoves that have been contrived by various makers for economising fuel, or he would scarcely talk of only "two buckets full of coarse slack" to effect the cooking, and there is nothing in his directions for use to indicate any peculiarity or superiority of management on which perfect success may depend. I have now occupied three houses, provided with these kitcheners, each of first-class make. In all cases they were tried with perfectly clean oven plates, and a brisk fire, the oven damper alone being left open. and the front door closed, so as to prevent the intrusion of cold air-so this is not "the secret of success." The end in each case was, that on account of the difficulty-if not the impossibility-of getting a quick oven, a supplementary cooking stove was with a small fire that the Leamington ovens were set up, the ovens of which were so quick and effective not afterwards employed on baking days. I have Leamington ranges. I found it not one bit better just taken a new residence, having also one of these or more efficient than the preceding ones. I should have done as before, and got a portable cooking stove, but could find no convenient place for it; 80, fearing that I must forego light pastry (a sad depri vation for me), I was driven to the necessity of doing something to render the existing oven more effective,

and as the remedy is a very simple one it may be of use to some of the readers of the ENGLISH MECHANIC in a similar predicament. The first consideration is the cause of the inefficacy of the oven of the Leamington range, as it seems unaccountable that when the whole heat of a very brisk fire is carried round the plates at the top, the side, bottom, and back, it should fall so far behind others in quick and effective baking. The heat at its first onset enters a large cabic space over the oven. The greatest portion is uselessly absorbed by the top of the range itself, which gets tremendously hot, and there is plenty of time here for this waste of heat by apward absorption, as the current is slow in such a capacious channel. Moreover, the rush of air from the front of the grate throws most of the flame and beat towards the back, where it is least required. We have here the top plates, acting as great heat absorbers and wasters, and the crown of the oven (which speedily gets covered with soot and light shes), most ineffective for heating the contents by downward absorption. By this alone nothing could be cooked at the bottom, and the residual beat that arrives there at last is barely sufficient. The first thing I did was to prize off a cast-iron baffle-plate that was lightly fixed to the top of the oven, and Dearly half covered the crown plate. I next laid in bricks close from the back plate over the top of the oven, well caulking and filling in all the crevices between the bricks and plates, till a channel was left scross the front 54in. wide. Through this passage the whole beat now makes its way. By this means only a small portion of the top plate of the range absorbs beat, but still it is amply sufficient for boiling. And where the bricks cross the pot-hole they are chamfered off, to allow a little flame to veer off to this locality, but this is not of much consequence. Now all the heat is brought over in front of the oven, where it before was liable to get cold, and is consequently most required, and all that is saved at the top goes round to increase the heat at the sides and bottom. Before this alteration it was impossi. ble to bake a joint in what I consider reasonable time. The improvement is most remarkable, and the range now acts so satisfactorily that we have abandoned the idea of taking it out, and replacing it by another form that we have before proved to act more effectively. It is very easy to sweep out the channel in front by passing the brush between the top bars of the grate.-F. H. WENHAM.

can be used as an open fire stove when not required little fishing village rather more than midway distant.
for cooking. The size of the fire can be easily regu. Padstow is a quiet pretty place, and the "Com-
lated as may be required, and is always kept close mercial" is the cheapest, most comfortable, and
to the hot plate, which is heated by actual contact cleanest hotel I stayed at while holiday-making.
with the burning coal even when the fire is small. From Padstow I went by bus to Bodmin-road
The oven is heated by two flues direct from the fire- Station (about 18 miles, fare 4s.). I should have
one over the top, and one underneath the bottom. liked to have walked on down the coast from Padstow
to Newquay (about 19 miles), and inspected on the
The oven can be heated from either of these as a
top or bottom heat is required, or they may be used route that wonderful geological curiosity, the Bed-
simultaneously, heating the oven regularly in all rutban Steps, but could not spare the time. From
parts without undue intensity of fire. No difficulty Bodmin-road I went by rail to Truro, and thence to
is found in baking bread on the oven bottom, and Falmouth. The latter port is to my mind the most
the quantity of fael (for which rough slack is per- charming sea-side place in the county, and the trip
fectly suitable) is less than half what is used in a up the Fal, back to Truro, in the "Resolute"
Leamington range of the same cooking capacity. I steamer (fare, 18.), was about the most enjoyable
lately saw a small Eagle range at work. It had a incident of my trip. Truro is well worth a visit of
large piece of meat and a pie cooking in the longer duration than mine, which lasted but a few
ovens, 2 chickens roasting before the fire, and 4 hours, when I took train again to Penzance. I was
saucepans boiling on the top. The lady using the disappointed in the town, which is dirty and mean-
range informed me that she did the whole of this looking, but the sea and the surrounding country
cooking with half of a small scuttle of small coals.- more than atone for this. St. Michael's Mount, the
Lizard, Scilly, and the Land's End can all easily be
FORWARD.
reached from Penzance, and you can return to

SIDE

[33572.]—Oval Top Trunks (U.Q).—Shape 2 Plymouth either by rail or steamer. I can say little

END OF TOP

pieces of in. stuff like drawing.-TELESCOPE TELE
[33587.)-Steel.-Huntsman's is the best I know
of. It used to be 18. 6d. per lb., and could be got
in Ann-street, Birmingham.-CHELT.

[33697.]-Metheglin.-This drink differs from
mead, which is made by boiling honeycomb in water,
and fermenting. Metheglin or hydromel is pre-
pared by stirring one hundredweight of honey with
24 gallons warm water, until dissolved. Next day
add a pint of yeast, previously boiled in a gallon of
water with a pound of hops; water is added to make
1 barrelful. It is then allowed to ferment with the
usual precautions adopted for other liquors. It con-
tains 7 to 8 per cent. of alcohol (Cooley).-T. P.

[33698.]-Dialyte Telescope.-This instrument was fully described in No. 515, and there is a long letter from Prof. H. L. Smith, of Hobart College, N.Y., in No. 522, giving an account of how he made several dialytes.-AN 8IN.

[33706.]-Mining.-In this question the heading is a case line to a triangle formed by the length of the seam of coal from the point above the bottom of the pit (25 yards) to the place at which, through its incliuation, 30°, it will be intersected by the heading driven truly level in front of the dip; this part is the hypothenuse, and the perpendicular is the distance perpendicularly above the bottom of the pit to the coal seam. (See accompanying illustration.) The

COAL SEAM

HEADING 43-3 YDS

26 YDS

[39570.]-Leamington Kitchen Ranges.-The
correspondent in your issue of the 23rd ult, signing
himself "L.," states that the defects complained of
in the Leamington range arise from want of clean-
liness and other mismanagement, and that, if pro-
perly cleaned, and intelligently used, it is an
economical cooking stove. This has not been my
experience, and I consider the principle on which
these ranges are constructed such that, however well
they are managed, fairly satisfactory results are
only arrived at by virtue of an extravagant con.
sumption of fuel for the amount of cookinz per-
formed. The principal errors in construction I
complain of are as follows:-1. Almost the whole of
the flues being constructed of brickwork, even in a
Leamington range of the best quality. you are
entirely at the mercy of the bricklayer who fixes it
as to its performance. Most of the workmen who
undertake to fix these ranges put in the flues entirely
by the "rule of thumb" as to their sizes and posi
tions for beating the oven and boiler. With any
defects in these the range will not work even fairly
well. But, even should the range be properly fixed,
the constant expansion and contraction of the iron
work of the range causes the brickwork flues to leak
and admit streams of cold air into the flues, by length of the heading may then be found by using
which the ovens are cooled considerably. 2. For a the following trigonometrical proposition: In any
Leamington range to work fairly well the fire-box plane triangle as one of the sides is to the other so
must be always full of coal. If the fire-box is allowed is the sine of the angle opposite to the former to the
to burn below the upper bars, cold air is drawn into sine of the angle opposite to the latter; .. sin. 30°
the flues, over the top of the fuel instead of through
sin. 60°: 25 yds. length of heading, or
5: 866: 25
it, cooling down the ovens at once. A door is some-
times used, which partially obviates this defect; but
even then the top of the fire is so far below the hot
plate that the saucepans at some little distance from
the fire soon stop boiling. A false bottom grate is
frequently used to meet this difficulty; but it is a
bad makeshift, as the two gratings placed one above-AAMDAL.
the other cause the ashes and clinkers to accumu-
late, and stop up the air passages. If they are not
constantly cleaned out imperfect combustion, with
Consequent waste, is the result. 3. Another diffi-
culty with this range is that the top of the oven is
always very much hotter than the bottom. In get-
ting the bottom of the oven sufficiently hot to bake
pastry or bread the top becomes so intensely hot
that 2 or 3 inches of it are of little nse. This causes
a great waste of fuel, as well as inconvenience in
cooking. The great intensity of the fire necessary
for getting the bottom of the oven bot rapidly
destroys the iron plates, bars, and fire-brick, so that
frequent expense is incurred in their renewal. I
quite allow that the Leamington range is a great
improvement on the old open-fire cooking stoves
which were formerly used; but I do not think that
any one who has given any attention to cooking
stoves will say that in ranges of this class we had
reached perfection, and might rest and be thankful.
There are now being manufactured several ranges
which are far in advance of the Leamingtons. One
of these the Eagle" range, which is in very
general use in Birmingham and environs-seems to
be free from most of the defects inherent to the
Leamingtons. It requires no brickwork fixing, and

25

•5) 21.650

43.3 yds. length of heading.
[33712]-Vacuum Engine.-No, a waterfall
will not produce vacuum "enough to work an
engine, but it might be made to work an engine, a
water-wheel, or a turbine.-BRINJES.

[33732.]-Phlegm in Throat.-"Bell", could
doubtless get his recipe transcribed-i e., copied out
in plain writing-by some chemist (I have often
had such done, and have ever found perfect readi-
ness on the part of chemists to do this), and publish
it in "
ours. I am myself also a sufferer from
this complaint, and should be much obliged, as
dare say many others would, if help could thus be
rendered.-E. W. A.

"

I

[33739.] — Brass.- Perhaps an answer to this query may be found in the fact that metal is cheap and that old brass will sell for only half what it used to fetch. Market quotations are not to be relied upon. for brass sheet is quoted 9d., whereas "F. W. S." says 61d.-M. S. K.

in favour of hotels, except the one mentioned above; the others were dear except at Penzance, and that was cheap and nasty.-TRELLIE.

[33795.] When Work on Clockmaking. Stylus says that "the only work on this subject is Reid's treatise," I suppose he means the only work he knows of, and overlooks the admirable work by Sir Edmund Beckett Denison in Weale's "Series" on "Clock and Watch Making."-KELBY.

[33803.1-8lide-rest Boring or Inside Turning Tools.-You cannot do better than make the plain inside tools-viz., these for simply boring cylindrical holes, an exact copy of the cutting part of an ordinary twist-drill. Take one of these, and try it as a turning tool, and observe how perfect its action is. For brass you may similarly copy an ordinary flat drill. If you have a L-shaped undercut groove te turn you must of course have a pair of right and left square-hooked tools, which if left too rank you will find addicted to sticking into the work. This is cured by slightly bevelling away the too keen chiselshaped cutting edge with a slip of oilstone. I am sorry to have delayed answering so long. It was "D. H. G." who first pointed out to me what a fine tool for boring a twist-drill makes. Whilst on the subject of twist-drills I may say that the first I ever saw in action was some 30 years ago on the occasion, I think, of my very first visit to Mr. Wilkinson, whose tools will be all sold off by the time this letter appears in print, and it was being used for drilling a large division plate for a clock-maker, the holes having to go clean through the plate, on account of its being used in a horizontal position, in order to avoid their being clogged with the cuttings from the brass wheels.-J. K. P.

[33838.]-Lighting Mines by Electricity.-I am not aware of the use of the electric light in any of the pits in the Midlands, neither do I ever remember reading of the use of it for the purpose. Besides, there would be too much difficulty in providing lamps for every collier, and a central light would be useless to more than three-fourths of the men. Nothing as yet is better than an oil or candle flame in a safety case. These can be carried easily, and can be used anywhere with infinitely less trouble than electrical vacuum lamps.-W. J. LANCASTER.

[33851.]-Nitrate of Silver.-About the simplest way to remove the silver from the solutions will be to add hydrochloric acid to the mixture, and thus obtain a precipitate of chloride of silver; then dissolve the precipitate in ammonia, and again precipi. tate with nitric acid; dry the precipitate, and fuse on charcoal, with bicarbonate of soda in the reducing You will then have beads of pure silver. flame. The colour of bath solution was due to iron, which, no doubt, was due to the tin still used. I have found the same colouration repeatedly when using water distilled in a tin or iron vessel, but never when the water has been distilled in glass vessels.W. J. LANCASTER.

[33853.)-Horse-shoe Electro-Magnet.-1st and 3rd bad, therefore don't attempt them; 2nd by far the best. The thickness of wire coil may be equal to the diameter of the core. Thus, if the core is in., then have a bobbin with in. depth of wire round. This will give the best results you can obtain.-W. J. LANCASTER.

[33854.]-Magnetism.-There would be an alteration in the magnetism of the bottom end of a telephone magnet, but not sufficieht to cause a cur. rent to be induced in a bobbin of wire on it. Telephones have been made, using up both ends of the magnet, but they are in no way superior to the ordinary form.-W. J. LANCASTER.

[33859.]-Tuning Fork.-All tuning forks are not alike, and, although there have been many attempts to obtain a uniform pitch. such a result has not yet been obtained. The ordinary fork (C) would give 512 vibrations, whereas the (C) fork recommended by the Society of Arts gives 528 vibrations. Again the (C) of the Italian Opera is 546. There are others varying between 506 and 546; but the Society of Arts' fork is about the best to use, although it is 10 below ordinary concert pitch-538. For scientific purposes the 512 fork is used in preference to either of the others. If it would be of any service to you, I could give you the pitch of most of the Continental conservatoires.

[33792.]-The Cornish Coast.-I have just re-
turued from a trip along part of the route you in-
quire about. I started from Launceston by coach to
Camelford (16 miles, fare 48), walked to Tintagel
(8 miles), walked thence along the coast to Padstow
(about 16 miles), stopping to rest at Port Isaac, a quaint W. J. LANCASTER.

[33861.]-Object-Glass of Telescope.-Some pouring off immediately after the rougher and 7ft. wheels and cabs. No. 1,198 bears date August,

heavier particles have settled, then allow the parti-
cles in suspension to settle. Keep this, and wash
again; then repeat the process, and use the deposited
emery in the order of washings, the finest to finish
the lens with, and when grinding save all the emery
you can, and subject it to the same washings.-W.
J. LANCASTER.

one has lost the double concave lens which formerly
went between the two convex lenses you now have.
These lenses are useless to you. and I am afraid you
cannot bave them repaired. Still, by sending them
to a good optician, he would tell you directly he saw
them. Dollond used to make his object-lenses of
three glasses, and uncemented.-W. J. LANCASTER.
[33862.]- Mixed Gases for Lantern. - My
[33883.]-Ammonia Direct from Gas Liquor.
answer is "Don't." If you want to burst the bag,-Having use for liquid ammonia I want to produce
break your leg, or damage the furniture, then do. it direct from gas liquor without first forming the
But, apart from making a joke of it, I must warn sulphate. It is at a gas-worke. The make is about
you not to attempt an experiment in the direction 200 tons at 6 degrees Twaddel. I am told it is best
you are thinking of. I could tell you how to use the to heat liquor in still, and when turmeric paper is
gases mixed, as you suggest, with partial safety, but not affected open lid and add some lime, and work
the risk is so great that I will not give the method. again until all is driven off. Is this the best way.
By all means use two bags or one bag and a pipe and will it require gearing to agitate the mixture if
from main.-W. J. LANCASTER.
lime is used? Is it best to heat by steain or fire, and
is it necessary to have worm in cold-water cistern to
cool ammonia gas before absorbing it in water, or
is it sufficient to have the absorbing vessel sur
rounded with water only? If "Ploni- Almoni
will kindly give a full description of the apparatus
best suited for the above requirements, and the
yield of ammonia per ton of gas liquor, it would be
useful to me, and perhaps many of the subscribers.
-W. T. KER.

a

[33863.]-Apparent Divergence of the Sun's Bays.-For a moment suppose we are standing on railway-bridge, and looking up the line we shall notice the apparent tapering of the lines. If we turn round we find the down lines have the same appearance, due, of course, to perspective. Now, with but little imagination I think we shall readily see the reason of the apparent divergence of the sun's rays. and after going over your head the convergence of the same rays. The rays on either side of you appear to be foreshortened, but I think if you remember that all the rays are parallel, it would be an easy matter for you to see them so.-W. J. LANCASTER. [33865.)-Rowing. The proper way to row a boat is, in pulling, to have the blade of the oar just below the surface of the water in a perpendicular position, and in pushing to have the blade of the oar just above the surface of the water, and in a horizontal position. The first, to offer the greatest surface to the water, the last to offer the least to the atmosphere. This applies to all rowing, although it cannot be well carried out in those small boats in which one man rows with two oars or sculls, because he cannot have his eyes on both sides at once. Moreover, he has to watch some object, so that he may guide his boat, for in such cases rowing and steering are generally done by one person, but he will still feather his oars for the only and sufficient reason given above. There is no difference between either river and sea-boats or river and sea rowing, except that there are small pleasure boats and amateur rowers. The most general boats are those belonging to ships, which are used both in rivers and at sea when required-viz., a gig, a pinnace or jolly boat, and the long boat. The oars are mostly alike, except that sometimes those of the gig are lighter. They average 10ft. or 12ft. long, with blades 5in. or 6in, wide, and to use them properly the rower must keep his eye upon them. The rower who does not feather his oar, and who dips it deep in the water, and lifts it high out of it, bears the same relation to boating that the man does to riding who mounts his horse throwing his left leg over and shows daylight between himself and the saddle when trotting.-BYR.

[33873.]-Pancratic Eyepiece.-I answered this question on p. 582, number of query, 33518. Beside the method there given, you may determine the power by obtaining foci of the four lenses, and their distances apart; but the calculation is so long that I have not thought it worth while to give it. You may roughly obtain the power by measuring the enlarged diameter of a small square or number of squares, first, with the single lens, and then with the eyepiece.-W. J. LANCASTER.

[33874.]-Lightning Conductor.- Under the circumstances, I would not erect a conductor. You might run a copper band around the largest tree, up as high as the roof of house, and then into ground to a large sheet of iron; but this, although it might be of service, is hardly worth the cost and trouble of erecting.-W. J. LANCASTER.

[33875.]— Spiders' Lines. Get one of the thread on to the end of a stick, then, by a gentle smallest spiders you can find, allow him to fix shake let him fall, say a foot; he will then have spun a fine line, and you may at once fasten it on to the diaphragm.-W. J. LANCASTER.

"

[33890.]-American 8-day Striking Clock.If Seconds' Practical Watchmaker" will pardon a disciple of his art, or at least of clockmaking, I will suggest to "J. L. H. S." that he can clean his clock without taking to pieces, by washing the flat works all together as they are with benzoline or petroleum spirit. This will most effectually clean out all the dirty oil. &c., even in the holes in which the pivots work, and after a good swilling all he need do is to put it in a warm oven or before the fire for a few minutes till the benzoline has evaporated. He must not put a light near the benzoline whilst using it, as it is very inflammable. I use a dinner plate and small brush for the job, and find it saves a great deal of labour and time. After it is all warm and dry, oil the pivots and pallets and springs with a is often used-and it will go again as well as ever, little best salad oil-olive oil that is, not hair oil, as If it must come to pieces for any repairs it is a good plan to tie a string or thin wire round the mainsprings when the clock is nearly wound up: then they will not expand all over the place when taken out. But the string must be a strong one, or it will break. I can answer for the methods given above from some considerable experience in that sort of clock as well as others.-AUGUSTUS.

[33896.]-Polishing Marble.-" Jack of All
Trades" replied to this query on p. 663, last vol.,
rather briefly. Before using the putty powder-
which must be kept moistened with water-the
marble should be particularly well rubbed with
snake-stone until all the scratches are thoroughly
out, as it is upon this "honing" that a good polish
chiefly depends. Will " J. L. H. S." be good enough
to say what cement be used to stick the pieces of
marble together ?-CLYDE.

[33904.]-Seeing the Bottom of the Sea.-You
may readily see the bottom of the sea by making a
simple telescope tube about 3ft. long, and of a taper
form from lin. diameter at the top to 5 or 6in. at
the bottom end. You must cement either a piece of
plane glass or a double convex lens
With the latter lens you would be able to see (in
or 6ft. focus
clear water) to a depth of 100ft. or more. If the
water is very transparent you might have a shorter
focus lens, and a concave lens at the eye end, thus
converting it into a simple form of telescope.-W.
J. LANCASTER.

[33907.]-Sulphuric Ether - Also called di-
ethylic sulphate, or neutral ethylic sulphate

was discovered in 1848, by Wetherell. It is prepared by passing anhydrous sulphuric acid into ether, conThe liquid after a while acquires a syrupy consistence, a tained in a flask surrounded by a freezing mixture. and must then be shaken up with an equal bulk of ether, and four times its bulk of water. After settling, the upper layer consists of sulphuric ether, which must be separated from the lower by means of a shaken up with milk of lime, to remove the excess of displacement flask. The ethereal liquid is then sulphuric acid, and part of the colouring matter; then washed with water, filtered, and the ether dis tilled off. The oily mass is then removed into a basin, washed with a small quantity of water, the last portions of which are removed by strips of bibulous paper. after which the liquid is dried in vacuo over H2SO, (Wetherell). Sulphuric ether is an oily liquid, colourless when pure, and has a sharp taste; spec. grav. 1.120.-T. P.

[33877] Microphone for Deafness. The and I am afraid it will be a long time before it can be microphone is at present useless for deaf persons, of service. Telephonic sounds are much weaker than the sound of the voice through a speaking tube, and until they can be amplified the microphone and the telephone will be of no service to a deaf person. I may, however, say that a conversation by sounds may be carried on, because some of the sounds produced by the microphone are peculiarly loud, and by a code of sounds being learned, a conversation could be carried on, the only difficulty being the learning of the code by the deaf person. A few weeks ago a gentleman heard distinctly the sounds produced by my microphone, although he had not heard before for over 20 years with that ear.-W. J. LANCASTER. [33879]-Photographic.-Well clean the plate with powdered French chalk, and the collodion will adbere. Your bath may be a little too acid; test it with litmus paper, and if too acid make it up to double the quantity with new bath.-W. J. LAN[33882.]-Lens Grinding.-Your tools are too small altogether. They should be much larger than the lens, or you will be unable to obtain a good figure. The emery should be repeatedly washed,

CASTER.

1861; No. 1,199, Nov., 1881; and No. 1,200, May, 1861.-MURANO.

(No. 2, &c.) I have seen belonging to this company [33911.]-8.E. Engines.-All the single engines have inside cylinders and outside framing, and the boilers have not flush-topped fire-boxes.-MURANO. plane, at lower end of which grate, C. Both are [33917.]-Burning Sawdust.-A B, inclined closed in by arch, G. M, fire door; N. ash-pit. A small fire is lit on C, and kept up till dust is fully ignited. The sawdust is fed in as needed through H. The dust spreads itself over the plane, A B, and

covers a part of the grate, C. The fire on C ignites the dust, which then burns along its upper surface. The holes, W W, are partly to insure downward movement of the dust, in case of stoppage, by inserting stoking iron, and also for supplying air to the upper stratum in case greater intensity of com bustion is required. The grate must never be quite covered with sawdust. As a good deal of ash is formed in the flues above A, provision should be made for easily cleansing them.-A. W. E.

with coal dust and gas tar; or if you burn it with s
[33917.]-Burning Sawdust.- Try mixing it
coal fire, coal dust and clay mixed with the sawdust
and water enough to make a very stiff paste, and
then made into balls by hand, and rolled in dry coal
dust and dried, might answer the purpose.-
MURANO.

lurgy. You will save time, money, and temper by
[33919.1-Size of Battery for Electro-Metal-
buying either Gore's "Electro-Metallurgy," or
Sprague's "Electricity;" then read thoroughly the
chapters on electro deposition, and you will be in
better form to ask
your queries exhibit not even an elementary know.
common sense." At present
ledge of the subject, and I can assure you it would
be time and space wasted to attempt to give the
information you ask for.-W. J. LANCASTER.

water, 8oz.; beeswax (genuine), 6oz. Mix with heat,
[33920.]-Furniture Polish.-Pearlash, loz.;
and add sufficient water to reduce it to the con
sistency of cream. For use, add more water, and
spread it on the wood with a painter's brush. Let
it dry, and polish with a hard brush or cloth. If
white wax is used it may be applied to polish plaster
casts, statues, &c. 2. Melt three or four pieces of
of boiled oil, and boil together for 1 hour. While
sandarach, each of the size of a walnut, add 1 pint
cooling, add 1dr. of Venice turpentine, and if too
thick a little oil of turpentine also. Apply this all
over the furniture, and after some hours rub it off.
Rub the furniture daily without applying fresh
varnish, except about once in two months. Water
does not injure this polish, and any stain or scratch
may be be again covered, which cannot be done with
French polish.-DICK.

[33923.]-Circular Cog-wheels.-I trust Fig. 1 will show in a simple manner that these cannot properly gear when turning eccentrically. As the of their peripheries in equal times (though each teeth of the two wheels must be the same size tooth has a different rate of revolution dependent they have evidently to pass through equal ares upon its distance from the fixed centre). Let the circles in Fig. 1 represent the pitch-circles of the evidently cut off an equal arc from each circle. Now wheels. Now from the point where the circles touch, with the same radius mark off P P', which will set off the fixed centres, CC, upon which the wheels the dotted arcs, representing the paths of revolution are to revolve. and with radii PC and P'C' produce of the respective points P and P. And as the ares between P or P' and the point of contact are equal (or otherwise stated, have an equal number of teeth) they must reach the points p p' on the line of contact both at the same time. But the above construction [33908 J-Concrete Buildings.-" Khoda Bux" intersected each other; for this reason, eccentric shows that before that time the pitch circles have (where is he?) gave a deal of information on this circular wheels cannot properly gear together. subject about five years ago. I would give As. Extending this construction it would be easy to find phalt" the numbers and pages, but I feel "kinder the centres of circles in their second position, but the fritened" when I look at my pile of unbound construction of the whole circles would only compli MECHANICS, 3ft. high.-MURANO. cate the illustration, and prove no more than the ing No. 1,199 at the Exhibition of 1862, but being their relation to the first position of the wheels. The [33910.]-L. & N.W. Engines.-I remember see-second position of two points in those circles, with only five years old, I did not make sufficient notes to 2nd position of any other point may be found in a simiCaithness, and Maberly are all stationed at the intersection would have been at its maximam. At answer the first part, but I beg to say that Delamere, lar manner. Had I chosen an arc of the circle their Camden or No. 1 shed, London. "Egeria" says page 663 E. R. Dale tells us as a fact, he finds two they are not Bloomers; as there is no difference lathe wheels of 60 teeth each revolve together when externally, will he kindly say what it is? They have turning on screws through the keyways. This, I

[33988.)-Speed of Trains. There are not enough conditions declared in this question to limit the answer; the solutions that may be given are consequently infinite. The only thing apparent is the difference in speed between the two trains, and even here the question is not explicit as to the meaning of the word, It may mean that pass." the time of passing is the period between the moment when the engine of the express is abreast of the engine of the goods and that when the tail buffers of the express are abreast of the head buffers of the goods engine; or it may mean the period between the moment when the head buffers of the express are abreast of the tail buffers of the goods and that when the tail buffers of the express are abreast of the head buffers of the goods. Assuming the latter case to be that intended, it is evident that the speed of the express exceeds that of the goods by 2 x 88 yards in 18 seconds = 20 miles per hour. Beyond this we have no clue whatever to the time or distance at which the passing took place, and consequently none to the speed of either train. The goods may have barely crawled a mile from the station where the express starts, or it may have gone 20 miles or any distance above or below either limit.-COMMON SENSE.

[33989.]-L. & N.W. Engines.-Besides the "Marano" mentions, No. 1,006, scrapped engines Prosperine, has been scrapped. Her date, I think, was about March, 1861. The Clyde, No 833, is a oft. 8in. coupled. Some of the goods engines have 7ft. 6in. single, outside cylinders, and No. 830 is a the date put on the regulator quadrant, but not all. -TAMERLANE.

[33989.]-L. & N.W. Engines.-The number of Delhi is 1.674, and her date April, 1868.-W. J. S.

[33989.]-L. and N.W. Engines. - The total number of Bloomers that have ever existed is 74, counting McConnell's last three. Those scrapped are 613, 623, 624, 853, 855, 856, 890, 1008, 1007. The date of 613 and 624 was 1854. They never had any