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the attention of ironmasters, even in this as the possessor of the largest supply of the
country, where coal is cheap and good. It fuel, we must look to American ironworks
is asserted, then, that the efficiency of for further information on the subject.
petroleum in puddling and heating furnaces
is from four to six times greater than that
of coal, weight for weight; and we know
from Admiral Selwyn's experiments, and
those made at Messrs. Barnes' works, that
the dead oil used here evaporates under
suitable conditions 201b. of
water per
pound of oil, and sometimes more (see
Admiral Selwyn's letter, p. 316, Vol. XXIV.).
Mr. H. Aydon, who has had abundance of

y. In order to show conclusively how valueless is this "Frame-Trunking," I will take and analyse so much of an ordinary average Instrument as is sufficient for the purpose; the Organ selected is that built in 1865 by Mr, Henry

THE ORGAN: A COMPREHENSIVE Willis, for the Episcopal Church, Hoddesden,
TREATISE ON ITS MANUFACTURE,
PROCURAL, AND LODGMENT.*

PART

BY JOHN WATSON WARMAN,
Associate of the College of Organists, London.

representative one as to design and size, also as Herts; and it is chosen as being a thoroughly

the work of an eminent Maker, and itself a really excellent Instrument.

z. The Organ is set out for 19 Sounding. I.-GENERAL TREATMENT IN Stops on two Mans. and Pedale, all the ManualStops-with three exceptions going to CC; the Manual Soundboards, Swell-Box, and Pipes are

MANUFACTURE.

the average

entirely carried on a Building-Frame, having for its uprights four solid Pine or Deal Posts, each 3 x 23. The whole of this Frame is of the most reliable and excellent design.

[42, a.] Now, let us see what would have been involved had Mr. Willis taken it into his head to adopt the "clever device" that has so excited the admiration of Mr. Hopkins. The Great and Swell Trunks are 12 x 5, and 11 × 4 respectively in exterior admeasurementthe Posts; this amount, therefore, must be in other words, more than five times the size of substituted for the area of two at least of the those at opposite corners to be of different sizes, latter, and as it would be inconvenient to allow

the whole four may be considered involved in the running straight to the Wind-chest (to have the enlargement. But, again, to allow of the wind Horizontals also furnishing Trunks is out of the question, as the required size on plan would be absolutely out of question), two of the Posts must run higher than the Horizontals. And yet, once more, these latter ought by rights to run in and "home" to the opposite or farther inner face of Trunk-Post; this necessitates extra size in the latter, to prevent the Horizontal obstruction unduly diminishing the aperture.

a. a. Now, only up to this point a great deal more will have been expended in labour, room, and material than can possibly be got back again. But we have not yet much more than commenced: the ends of the two Posts must be carefully sealed, then the communication

remains to be made; the lower Trunk must be Bellows-band to the vertical Post (the work on "Twisted," so as to lead from the horizontal

experience in burning liquid fuels, stated t. IT may of course be fairly argued that the on p. 293 of the volume above-mentioned word "direction" does not necessarily that the oil ceases to be cheaper than coal mean or assume that anything advantageous when it rises above 14d. per gallon, and as is involved, inasmuch as direction may be bad, the supply is not always constant in some as well as good. The perfect truth of this is districts, steam-users cannot afford to run sufficiently exemplified by the "retrograde the risk of having to use coal. Although advance" just instanced; and it is only fair to the oil has been suceessfully employed for state that Mr. Hopkins does not at any portion about ten years, it may be doubted whether of his Book distinctly lay down that the the best method of utilising it has been Organist is capable of beneficially "directing" adopted. As a rule it is blown into the the Organ-builder; and that he in many cases furnace in the form of spray, but in the of Instruments in which no "assistance" from -as on page 443-speaks in the highest terms most successful apparatus employed in America the fuels are converted into the any Organist is mentioned: but why use the gaseous state before reaching the combus-on page 465" from a Specification prepared by word "direction" at all? Why not say-as tion chamber. The purity and intensity of Mr. the flame thus produced renders petroleum Organist to the Chapel ?" an excellent fuel for iron and steel working, knowledge of the construction of this compli. u. If Mr. Hopkins has really mastered the the sulphur and phosphorus being more cated Instrument he should have realised long thoroughly eliminated, so it is said, than ere this that the Player is, as such, waterly by the Siemens' gas process. We have unable to afford the Builder any assistance what mentioned above that the present price of ever, except sometimes in a few little matters petroleum is about one dollar per barrel, so which may be termed Professorial Idiosynthat it probably costs rather more than crasies. In the drawing up of the Specification 1d. per gallon by the time it arrives at supposed, curiously enough, to be the the ironworks. It is doubtful whether at Organist's special province that price there is any economy in the use Builder has at least fifty times the experience of of petroleum, even in America; while it is the average Organist to guide him; and not certain that it would cost more if the oil only this, but being the Foicer as well as the were brought across the Atlantic. But Maker of the Instrument, he has an appreciaassuming that the gases obtained from tion of the relation subsisting between the Registers themselves and the circumstances petroleum, steam, and air eliminate sulphur under which such Registers are productive of and phosphorus more thoroughly than certain effects, of which the ordinary Organist those obtained from coal, it is obvious that does not even dream. it would be good economy to pay more for V. But this is not all; words often have-over fuel, in order to produce superior metal. and above their recognised and logical meaning Ironworkers in the United States are -a significance none the less real because a single twisted Trunk is equal to that of not now inclined to alter existing plant not sanctioned by strict rule: of such as these two ordinary ones); then, in the top Trunk a for the purpose of experimenting with the word in question supplies a very notable second "twisting (to bring it into correpetroleum, whatever they might feel example; and there can be no reasonable doubt spondence with the horizontal Chest) must inclined to do in more prosperous times; that the average reader of the words "built often be performed; and it will be a great chance after all if the Draw-action, or somebut the oil-owners may possibly take under the direction of Mr. -" would, in the the advice offered them, and set up smelt- absence of better guidance, certainly receive the ing, puddling, and heating furnaces, and so impression that, had not the Organ-Builder compel the ironmasters to adopt the use of accepted the benefit of Mr.'s kind offices, petroleum, by producing a cheaper and the result must have been a lower or less exbetter iron than can be obtained by means cellent quality of Instrument. of coal. The best furnace for utilising the w. I will now endeavour still more clearly to petroleum consists of several parts, and demonstrate what sort of "direction" the may or may not include the use of steam, average Organist is capable of; and what according to the purpose for which it is Instruments might be expected to result from such "direction." At para. 1,170 of Mr. intended. Where steam is used there is a super-heater with a coal fire, and over it is Hopkins's Work reference is made to an Organ shown by Mr. Hill in our Exhibition of 1851, placed a vapour-generator. The latter is so which had the chief portions of its Buildingconstructed that the petroleum runs over Frame constructed so as to serve as just stated and falls from a series of inclined plates, viz., for Wind-Trunks also. Mr. H. calls this and in its passage downwards it is vapour- the "climax of the simplification system," ised by the upward current of steam, and clever device," and as dispensing with "some he combined vapours pass into a chamber, of the most bulky cumbrances" left in the where they are supplied with the proper Instrument. quantity of air. The mixed gaseous fuel X. Now what are the plain facts with referthen enters the combustion chamber-a ence to the foregoing expedient? Simply, that ellular construction of fire-brick-where it is, as a rule, one of the most foolish to which the combustion begins, and is completed in a Builder can resort, not only failing to relieve the furnace beyond. The super-heater, the interior to any appreciable extent, but invapour-generator, &c., can all be contained volving a very large amount of additional work, a space of about the same dimensions as and also lengthening the wind passage; this last az ordinary boiler furnace; but modifica (although in the present writer's opinion of s of this apparatus would doubtless be very questionable disadvantage) being most d. To demonstrate this latter point, it may aired in the manufacture of the combined distinctly reprehended by Mr. Hopkins himself (see para. 97, first Edit.): and all this to get be mentioned that this particular Instru es for use in metallurgical processes, rid of one or two portions which in many cases ment, though much too confined, yet con. is a question whether the advantages obtained from the steam would be (see 143, n.), so far from being among "the tains an area of as much as 100 square feet; most bulky cumbrances" of the Instrument, while of the three Wind-trunks it possesses, one apparatus by the addition occupy a really excessively small area (compara--the Pedale-is (except a few inches at each tively); and are in no sense necessarily practical end) inside the bellows, and the two remaining -although of ample size-do not (see a, ante) per-heater. These, how obstructions at all. take up so much as one square foot area. for experiment, and And these are what Mr. Hopkins calls "bulky

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thing else, do not come in the way.

b. But we have not finished even yet. The Wind-chest proper will be as a rule-central, to allow of the Pallets being got at; they are so in the Organ in question: the entire Instrument is 10ft. deep, so that the Posts, which are of course at the extreme corners (for the sake of convenience in the Bolting), are really some distance from even the nearest point of Windchest; this distance therefore has to be retraced by the wind, thus making the journey, as previously said, a very roundabout one.

c. Now note, the area alone of the four Posts

as so enlarged, will be equal (if the Hori zontals "run home") to the Trunks and Posts combined in the ordinary arrangement; while the filling up of the corners of the Organ itself is often most inconvenient for Blowing-action or Bellows (it would be so for both in the Organ in question). In addition to this, the four complicated Trunks instead of two simple ones, the extra height and material of Posts, and the large amount of work generally, will mount up to a really alarming figure; and all to save two Trunks of fractional size (compared with the entire Organ area), and offering no practical obstacle whatever to the getting at any desired portion of the instrument.

cumbrances." Such talk as this can only be described as really lamentable.

e. It is only necessary to add that any modi. fication in the form of the Building-frame-with a view to bring it more conformable to the serving as a Trunk-will almost inevitably be to the injury of its simplicity and convenience as & Frame. It is right to mention that under some circumstances the elongation and second enlargement of the Post, and the twisting of the top Trunk, might be saved; but even this leaves the account considerably on the wrong side.

k. I think it may be confidently laid down that for a starting point, with a square Post, the foregoing size of 3 off a 3in. Pine or Deal Plank cannot possibly be improved on: it is nearly enough to the square not to be of wasteful shape, and yet will require no glueing up, or use of Timber stuff or Pitch Pine (see 35, m.). With larger Organs (say, over 25 SoundingStops), 4in. Pitch-Pine Plank may be used; with still larger ones, 5in. Timber; and with the largest of all 6in. Timber may be employed. Sizes between these may also be used, as 4 × 41, 4 × 5, and so on.

f. I now leave my readers to judge for 1. Smaller Instruments than, say, 18 Soundthemselves as to the probable value of the ing Stops may have Posts 3 x 3 plank; still opinions constantly passed by some Organists smaller, 3 x 24-pricked; smaller again, 24 × on the structure of the Instruments on which 2-pricked; then 2 × 2-pricked; then, 2 x they perform. If such a criticism as the fore- 2-pricked; smallest of all, 2 x 14-pricked. going could proceed from one who has written These will be all found convenient sizes, and an Organ Work of nearly 600 pages-one, more- involving the least sawing; yet nearly enough over, to which it would be idle to deny the to the square to be really economical. But possession of a certain amount of value-what none of them, remember, are for Chamber are we to think of such utterances and testi- Instruments,-for which see 43, z. (It will monials as are being given every day by shortly be seen, however, that it is rarely worth Organists who are not certainly known to whilet o furnish very small Instruments with a possess one particle of structural knowledge | Building-Frame at all). whatever?

g. The truth is, the notion of making the Building-frame serve as a Trunk is one that would naturally occur to any ordinarily intelligent Builder; only that he would generally realise in a few moments how much more would be lost than could possibly be com

(To be continued.)

ON A NEW PHENOMENON OF
STATIC ELECTRICITY.

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GALVANIC CURRENTS FROM FLOW OF LIQUIDS THROUGH TUBES. HE phenomenon here indicated was disphysicists have since engaged in the study of it the nature of the conditions under which these currents are generated has not yet been very clearly determined. That the intensity of the currents in general decreases along with the resistance of the liquid, and is generally dependent on the nature of that, has been established by several observers. The electromotive force, further, has been found propor. tional to the distance between the electrodes. But the results have been contradictory in reference to the cross section of the tube. While Edlund holds that the electro-motive force is inversely proportional to the cross section, Haga has theoretically obtained, for narrow tubes, Clark merely a decrease with increasing cross section. Further, Edlund found the electroto these, but for larger proportional to their motive force, for small velocities, proportional square; while Haga finds, in the case of narrow the pressure. tubes, the electro-motive force proportional to Lastly, Haga and Clark, in electro-motive force after coating the inner opposition to Edlund, affirmed a change of the surface of the tubes with various substances.

THE covered by Zöllner; and though several

pensated for: the arrangement of the Organ E. DUTER has submitted to the Paris an inverse proportionality to the radius, and

Academy of Sciences the description of Mr. Hopkins mentions-supposing he has cor- an experiment showing that in certain cases rectly described it-was most probably the re-electrisation can change the volume of bodies. sult of some little "fad" or fancy on the part of the Constructor, perhaps done as a thing that would sound clever to the ears of the "groundlings" of Organ-art-perchance to tickle a Jury. Had Mr. William Hill never done anything that showed greater "cleverness" than this, most assuredly would his reputation never have been what it was-almost world-wide. The strongest proof of the general worthlessness of the Arrangement as a saving, is the simple fact that although it must be by this time thoroughly well known, it is yet-even in this economical age-rarely or never resorted

A thermometer tube of large dimensions has
a platinum wire inserted in it. It is then
filled up with water and tinfoil pasted on the
outside so as to form an ordinary Leyden jar,
which is charged in the usual way. As soon as
it has received the charge the water descends
and continues stationary, whilst the charge
remains, but instantly takes its first level on
the discharge.
"the electricity remains only in the insulating
"As, in a condenser," he says,
plate it is natural to conclude from this
experiment that the glass expands," and he
considers this idea confirmed in the first place

his theory of electricity, in which the electric Edlund endeavours to explain it according to With regard to the ground of the phenomenon, current being thought to be merely a motion of the intermolecular ether, a current must arise

to, even by the Builder who seems to have given because the apparent contraction of the interior on motion of the liquid and so of the ether it

it birth.

h. It may be thought that in the foregoing I have expended a great many words, and a good deal of unnecessary warmth over a very simple matter. I have done so deliberately, and with definite purpose; I wish to state honestly and candidly the attitude I intend to adopt with respect to this question; and I have a second time gone at this length into it, in order that in future, when it is necessary to call attention to other erroneous or absurd utterances on the part of would-be Organdesigners, it may be clearly known that Lowever curtly or apparently dogmatically the remarks themselves may be expressed, they are always the result of careful and deliberate consideration.

the seat of electro-motive force in the boun-
contains. Clark, on the other hand, places
dary surface of the liquid and the solid tube
wall; for which view the influence of the coat-
these currents as friction currents.
ing seemed decisive. Zöllner finally regards

liquid is the same whatever may be the nature
of the armatures, whether tinfoil, water, saline
solutions, or mercury. To remove all doubts
he modified the apparatus by placing the
Leyden jar in an envelope of closed glass, ter-
minated with a thermometer stem and equally
filled by an electric condenser, the liquid enve-
lope in the form of an external armature, and
the surface of the interior glass is the insulat-
ing plate. This, according to anticipation, in-
creased the result on electrisation and estab-Annalen der Physik).
lished the fact that the water descends in the
thermometer tube of the inclosed jar, and
mounts in a sensibly equal quantity in the
measuring tube of the envelope.

As soon as the apparatus is discharged all
returned to its primitive state: the liquid that
i. And it must not be forgotten that such a had descended in the interior jar remounted,
method of expression as that of the paragraph and that which had risen in the tube of the
in question often carries with it much more envelope descended.
weight than the most carefully-written direct concludes that, during the charge of a Leyden
M. Duter, from this
eulogium possible: the aim of the latter is dis-jar, the interior capacity and exterior volume
tinctly seen, and allowance-even involuntarily increase.
-made for it; but an assertion given as a
matter of course, and without, as it were, any
visible effort, carries weight to the minds of
many because of that very absence of earnest- 1. We cannot attribute the observed effect
ness, the speaker being either really or appa- to an augmentation of temperature, since the
rently not the least anxious about the recep-discharge makes it disappear immediately in
tion of his dictum; giving it, in fact, as a matter
absolutely and entirely beyond question.

** POSTS AND RAILS.

We now return to the consideration of the actual size of the chief portions, commencing with the Posts or UPRIGHTS.

Not to have any doubt on the subject he proceeds to review the objections that may be made to it :

place of increasing.

2. We may speak of the electric pressure, bat it would be the same upon both faces of diminution of volume in place of the observed the dielectric, and then it would produce a increase.

1. It will be obvious that no exact diameter perfectly moisten the glass before electrisation,
3. We may say also that the liquid does not
can be indicated for these even for an Organ and that afterwards, in consequence of the
of given size, the general Lay-out and various attraction, it produces a more intimate contact,
other matters so very much affecting. Particu- giving place to an apparent contraction of the
larly will the length or height of the Posts them-liquid; but there the same phenomenon should
selves do this, for it will be evident that an be produced in the exterior liquid, which does
Upright perfectly rigid at 6ft. in length will be not occur.
very shaky if of 12ft., unless guyed or braced
laterally; and this point must therefore be
carefully considered.

perties of the positive and negative armatures;
4. We may again speak of the different pro-
but if the communications with the electric

These discrepancies led Herr Dorn recently to periments, if they do not fully settle the quesa fresh study of the phenomena, and his extion, have a special value, as having been made with wide tubes. (They are described in the

shall only remark that the measurement of the As to the nature of the experiments, we electric current was made with a galvano

mined by comparison with a normal Daniell meter, and the electro-motive force was deterelement. The 16 glass tubes, through which the water was forced under exactly measured between 49.7 and 300 15mm. The author sought pressure, had various diameters from 1.033 to 4.835mm., and the lengths of the tubes varied first to determine the fundamental question, rated by a free-water jet without inclosing whether an electro-motive force is also genewall, and special attention was paid to the continuity of the jet. This important point being settled in the negative, Dorn examined successively various influences on the excitation of electricity-viz., the pressure, the degree of separation of the electrodes, and the nature of the inner wall of the tubes. In this last series of experiments not only were the tubes tried, which did not materially alter different thin coatings of the inner surface of the cross section in wide tubes, but also the investigated, tubes which had long been filled alteration of the glass wall with the time was with water being compared with others newly cleaned.

up by Herr Dorn as follows:-
The results of these experiments are summed

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'My researches have proved-(1) that the mere motion of water does not produce a galarises in the case of flow through a tube; (2) vanic current corresponding to that which that even fortubes which do not satisfy Poisse

ville's law, the electro-motive force is proportional to the pressure; (3) that for wide tubes also the electro-motive force is dependent on the nature of the tube wall, and varies both in course of time, when the tube is filled with liquid, and on application of coating to the inner wall."

It is to be noted that the variation with the time did not always happen in the direction of decrease, and that, on coating with white wax, the galvanic current went contrary to the

motion of the water.

Further, the statement was confirmed that, with the same velocity, the electro-motive force is proportional to the length of the tube. To enter on a thorough discussion of the causes of the entire phenomenon, I hold to be premature, as the experimental material is still

too imperfect. So much, however, may be

looked on as certain, that the liquid motion, per se, produces no considerable part of the electromotive force, and consequently that the explanation given by Edlund, on the ground of his unitarian theory, is untenable.

On the other hand, the influence of the tube-wall is undoubted, and it is natural to place the seat of the electro-motive force (as Clark does) in the boundary surface of the liquid and the solid tube-wall. Still it remains doubtful whether we should think of it as produced by friction or by an action of contact. The latter supposition would connect itself with the explanation given by Quincke of the reciprocal phenomenon-viz., the transference of liquids by the electric current and the motion of suspended particles under its influence.-Der Naturforscher.

DYNAMOMETER FOR LOCOMOTIVES.*

TH

year, by an amount which will be fixed by the use
of the dynamometer.
3. In cases where trains are delayed, &c., the
dynamometer will show whether this was due to an
increase of tractive force, or to the fault of those in
charge of the train.

4. It enables the amount of fuel consumed, in
proportion to the work done, to be accurately
known, and the prizes for economy given to the
drivers to be placed on a rational basis. It must of
course be remembered that it does not give the
work done in moving the engine itself; but this
can be easily ascertained by other means, and is
not subject to much variation from differences of

wind and weather.

COMBINED CIRCULAR SAW, BAND
SAW, &c.

COM3
YOMBINATION wood-working machines are
in considerable request in small shops,
where the advantages of machinery, though
fully appreciated, are beyond the reach of the
proprietors. The Americans lead the world in
this branch of machine construction, for there
is a greater demand in the United States for
machines of the kind than in this country,
where, however, a change for the better is
observable. We illustrate a comparatively
simple combination of the band and the circular
saw, the invention of W. B. Beynon and B. J.
Webber, of Torquay, which has been recently
patented, and which, so far as the band saw is
concerned, possesses some useful features.
According to the patentees the invention con-
sists of a novel arrangement and combination

HE dynamometer is intended to answer the same purpose for locomotives as the friction brake dynamometer for ordinary engines. The instrument is fixed between the engine and the first carriage, and records, by means of a pointer moving over a face like that of a gas meter, the number of hectometre tonnes performed by the engine in anv given time. For this purpose the revolutions of one pair of wheels are measured by means of a worm fixed on the axle engaging with a small worm wheel, which is mounted on a long spindle, reaching from the axle to the recording apparatus between the engine and the carriage. Here the motion is transferred, by means of a pair of bevel wheels, to another small shaft, which carries a large disc. Against the face of this disc presses a small wheel, connected with a spiral spring, which, through a "ystem of levers, is extended by and in proportion to the strain on the draw bar. When this strain is zero the wheels rest exactly on the centre of the dise; but when the strain has any other value the wheel is pushed outward towards the circumference of the disc, through a proportionate distance, and of parts, together forming a combined machine it then revolves by friction with the same velocity as the portion of the disc at that particular distance which performs the functions of a circular saw from the centre. Thus it will be seen that when bench and operates as a boring apparatus, the speed of the axle is constant the revolutions of band saw, and saw sharpener, and also as a draw-bar, and when the pull is constant the revo- represents a side elevation of part of the the small wheel are proportional to the pull on the toothing and gulleting apparatus. Fig. 1 lutions of the small wheel are proportional to the machine, and Fig. 2 is an end elevation. The speed of the axle, or to the distance run by the circular saw table or bench is furnished with a train; therefore when both vary the revolutions of the small wheel are proportional to the product of guide, which is so arranged that it can be set those two the pull on the draw-bar and the distance instantly, there being a slot in the bed-plate, run by the train-i.e., in other words, to the work, in which the guide slides, and, when set, is The bed-plate, D, is done by the engine. All that remains is to connect tightened by a screw. this wheel to the pointer by a train of clock work, hinged at one end to enable the saw to be taken and the latter will then record the work done. out, and to give the advantage of a bearing on Various devices and precautions are described for each side of the saw, so that it may be run at rendering the principle efficient, and an account is a high speed without vibrating. The frame, H, given of experiments made with the apparatus on of the band saw is bolted to the circular saw the Archduke Albert Railway, in Austria. It was table. Its peculiarlty is in having a quadrant found, for instance, that the greatest variations in the resistance to traction took place in April and with a slot in it, on which is fixed the saw, May, on necount of the changeable weather; and, which can be so graduated as to take in any again, that the traction was less towards evening, size saw, and arranged to any bevel, so that the because the weather is then generally finer, and emery wheel can be made to cut the teeth at thara is less wind. The apparatus applied either to all angles. The table also is made to move at axertain the average work done during a long trip, any angle whilst sawing by means of a cam, so or the total work at some special part of the line. that timber may be cut at any bevel on either In the latter case the record must be noted at short side whilst in action. The emery wheel, M, is intervals, and the apsed observed independently. fitted on a shaft made of steel or other suitable The following important points, among others, may metal, and set in gun-metal bearings, which be determined by the use of this dynamometer: portional consumption of fuel may now for the first Limo be necurately ascertained.

gulleting and toothing apparatus is combined with the saw table it can be worked connected or disconnected as one and the same machine, and either by hand or power.

IMPROVED COPYING PENCILS. ENCILS made to produce marks from which PEN copies can be octained in an ordinary copying press, have usually the disadvantage that, consisting mainly of aniline, the colour of the copy faded very soos. Gustav Schwanbauser overcome this difficulty by doing away with aniline altogether. He prepares the pencils as follows:-101b. of the best logwood are boiled repestedly with 100lb. of water, and the decoction so obtained is evaporated down to 100lb. The liquid is heated to the boiling point, and small quantities of the nitrate of oxide of chromium added, till the bronze-coloured precipitate formed at first is redissolved in a deep dark blue colour. The liquid is now evaporated to the consistency of a syrup, and the finest levigated fat clay is added in the proportion of 1 part of clay for every 3 or 3 parts of the extract. To form a good mass to manipulate, a little mucilage of gum tragacanth may be used. The quantity of nitrate of chromium must be in the right proportion to the extract, as a surplus prevents an easy writing, and a deficiency prevents the easy solubility of the mass for copying purposes. No other salt of chromium will answer the purpose, as they all crystallise, and the crystals formed in the mass will cause the pencil to be rough crystallise; its combination with the extract of logwood is the most easily soluble and the blackest ink. The nitrate is prepared as follows:-201b. of chrome-alum are dissolved in 200lb. of boiling water. To the solution is gradually added a solution of

and brittle.

Nitrate of chromium does not

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carbonate of sodium of the same strength, till all the hydrated oxide of chromium has been precipitated. After subsidation of the precipitate the supernatant liquid is decanted and the precipitate sodium, as may be shown by the addition of a little washed with distilled water, till the filtrate does not contain any more traces of sulphate of kalium and solution of chloride of barium. To the precipitate collected on the filter are successively added small portions of heated pure nitric acid, previously diluted by its own volume of distilled water, in such quantity that on boiling a small quantity of the hydrated oxide remains undisssolved. In this way a perfectly saturated solution of nitrated oxide of chromium is obtained, containing no excess of nitric acid. This is a great advantage, since an addition of nitric acid to the ink changes its colour to a muddy red. Another advantage is, that no basic nitrate is fermed, and no excess of bydrated oxide is contained in the produced salt, as is the case in most other salts of chromium. Such basic salts form an insoluble compound with the extract of logwood, instead of entering into solution. The writing furnished by these pencils is easily transferable; it is of a penetrating jet black colour. Alkalies and acids are without any effect on the ink-Schweizerisches Gewerbeblatt.

THE SAWYER-MAN ELECTRIC LIGHT

HOME of the details of the Sawyer-Man electric

1 The actual power of an engine, and the pro- are carried on a slot lever, P, with a handle in light have been published in the United States

A The Labina of maximum load on inclines, &o., may be corrected and verified. The maximum loads should be varied, according to the season of the Altranted from a paper by II, KILLIcans in Die

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front; when working the emery wheel, M, is
adjusted by the rising and lowering of the lever,
P, which is truly balanced. On the same shaft
is carried the upper drum of the band saw, the
lower drum being carried by a movable arm, T.
The table is so connected with the quadrant, J,
as to give any angle to the cut. Though the

make the following abstract :-
by the Scientific American, from which serial we

:1

The production of light through the incandescence of a pencil of carbon or metal, forming part of an electric circuit and highly heated by its interna! resistance to the passage of the electric current. offers an entirely different field for exploration; and

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That portion of the current which is used for the regulator is also made to serve in the production of the light. A part of Mr. Edison's device for compensating for los in subdivision consists apparently in the utilisation for illuminating purposes of the resistance of the regalator, and of all other resistance outside of the main conductor, and part in the peculiar form of the conductor. The details are still a secret.

and has applications for nine others pending. Mr. Edison has obtained two patents in America, Specifications for a third English patent have

reached this country.

machine is expended in two ways-viz., 1st, In the resistance of the arc, it being much less in the overcoming friction and the resistance of the air; case in which the greater light was produced. The and, 2nd, In moving the armature of the machine heat in this case being evolved in less space, the emthrough the magnetic field, the latter of course perature of the carbons, and therefore their light constituting solely the energy available for produc- giving powers was considerably increased. A few ing electrical current. The greatest amount of remarks on the economical production of light from power expended in the first way was noticed to be electrical current may not be out of place. The about 17 per cent. of the total power employed. light emitted by an incandescent solid will increase This expenditure was clearly traceable to the high as its temperature is increased. In the voltaic are speed required by the machine. The speed there- the limit to increase the temperature is in the too fore required to properly operate a machine is an rapid vapourisation of the carbon. Before this point important factor in ascertaining its efficiency. The is reached, however, the temperature is such that the above percentage of loss may not appear so great, light emitted is exceedingly intense. No reliable bat when it is compared with the total work done method of measuring the temperature of the arc has in the arc, as heat, constituting as it did in this as yet been found. A well-known method of obtain- Replying to a letter in the Times, Dr. C. W. particular instance over 50 per cent of the latter, ing light from electrical currents is by constructing Siemens says:-" Captain Bucknill points out very and about 33 per cent. of the total work of the a resistance of some material such as platinum, forcibly that in the experiments carried out last circuit, its influence is not to be disregarded. In having a high fusing point, and heated to incandes- spring at the South Foreland, by Professor Tyndal! another instance the work consumed as friction was cence by the passage of a current. When platinum and Mr. Douglas, for the Trinity-house, great loss equal to about 80 per cent. of that appearing in the is employed the limit to its increase of temperature of illuminative effect was observed to result from an are as beat, while in the Gramme machine ex- is the fusing point of the platinum, which is unques- increase of electrical resistance of the metallic conperimented with, this percentage fell to 20 per cent. tionably but a fraction of the temperature required ductor through which the current is communicated of that which appeared in the arc as heat, and was to vapourise carbon. Were the falling off in the to the lamp from the dynamo-electrical machine. only about 7 per cent. of the total power con- amount of light emitted merely proportional to the This loss was relatively greater in the case of the sumed in driving the machine. In regard to decrease in temperature, the method last described Siemens than in that of the Gramme machine, for the second way in which mechanical energy is might be economical. Unfortunately, however, for the simple reason that the former machine had been consumed-viz., in overcoming the resistance this method, many facts show that the decrease in constructed with little resistance in its own coils, the necessary to move the armature through the the light emitted is far greater than the decrease intention having been to produce quantity rather magnetic field, or in other words, to produce of the temperature. Most solids may be heated than intensity of effects. Electricians will readily electrical current, it must not be supposed that all to 1,000° F., without practically emitting light. At follow me when I say that the internal resistance of this electrical work appears in the circuit of the 2,000° F., the light emitted is such that the body is the dynamo machine, or the size, thickness, and machine, since a considerable portion is expended in said to be at a bright red. At 4,000° F., the amount length of the insulated wire employed in its conproducing what we term the local action of the ma- of light will have increased far more than twice, struction, should always be made proportionate to chine-that is, local circuits in the conducting probably as much as four times that emitted at the external resistance, comprising the lamp and masses of metal, other than the wire, composing the 2,000° F. It is reasonable to suppose that with a its leading wires, in order to obtain a maximum machine The following instances of the relation further increase of temperature the same ratio of effect. It would be as wrong and wasteful to employ between the actual work of the circuit and that ex- increase will be observed, the proportionate in- a dynamo machine of considerable internal resistance pendel in local action will show that this latter is increase in luminous intensity far exceeding the in- to work through a circuit of little resistance no wise to be neglected. In one instance an amount crease in temperature. It would, therefore, appear as it is to attempt a greater external resistance of power somewhat more than double the total work that the employment of a resistance of platinum or with a machine of little internal resistance, of the circuit was thus expended. In this instance other similar substance, whose temperature of altera- such, for instance, as would be suitable for effecting also it constituted more than five times the total tion of state as compared with that of carbon is low, metallic precipitation. As an example of producing amount of power utilised in the arc for the production must be far less economical than the employment of electric light at a considerable distance I may here of light. In another instance it constituted less the arc itself, which as now produced has been esti-instance Sir William Armstrong's interesting appli than one-third the total work of the circuit, and mated as about two or three times less expensive than cation, who lights his library at Cragside success. somewhat more than one-half the work in the arc. gas. Indeed it would seem that future improvements in fully with a current produced by a waterfall 1,500 Of course work expended in local action is simply obtaining light from electrical currents will rather yards distant. A Siemens dynamo machine of the thrown away, since it adds only to the heating of be by the use of a sufficient resistance in the most smallest type is employed to generate the current, the machine; and since the latter increases its elec- limited space practicable, thereby obtaining in such and this is conveyed to the lamp and back again to trical resistance it is doubly injurious. The local space the highest possible temperature. Perhaps the machine by a copper wire of three-tenths of an action of dynamo-electric machines is analogous to the highest estimate that can be given of the inch diameter, suspended at intervals from iron the local action of a battery, and is equally injurious efficiency of dynamo-electric machines, as ordinarily posts, and representing a resistance of about 1 unit in its effects upon the available current. Again, in used, is not over 50 per cent. Our measurements or ohm. If a waterpipe or the metals of a railway regard to the internal work of a machine, since all have not given more than 38 per cent. Future or tramway could have been pressed into service for this is eventually reduced to heat in the machine, improvements may increase this proportion. Since the return of the current, one-half of the line the temperature during running must continually the efficiency of an ordinary steam-engine and boiler resistance might have been saved, or the distance of rise until the loss by radiation and convection into in utilising the heat of the fuel is probably over the light from the source might have been increased the surrounding air is eventually equal to the produc- estimated at 20 per cent., the apparent maximum to nearly 3,000 yards. This would, therefore, be the tion, and the machine will at last acquire a constant percentage of heat that could be recovered from the limit of distance to which the light might be carried temperature. This temperature, however, will differ current developed in a dynamo-electric machine in a town, where the water and gas pipes constitute in different machines according to their construction, would be overestimated at 10 per cent. The econo- a perfect return wire for any number of electric and to the power expended in producing the internal mical heating of buildings by means of electricity circuits. Sir William Armstrong now intends to work, being, of course, higher when the power ex- may therefore be regarded as totally impracticable. put up a medium-sized dynamo machine at the pended in producing the internal work is propor- Attention has, long ago, been directed to the use of source of water-power, and to utilise the smaller tionally high. If, therefore, a machine during dynamo-electric machines for the conveyance of machine as a motor for working the lathes and ranning acquires a high temperature when a proper power. Their employment for this purpose would other tools at his experimental workshop during the external resistance is employed, its efficiency will be indeed seem to be quite promising. Since in this daytime, while reserving the faculty of lighting his low. But it should not be supposed that because a case one machine is employed to produce electrical principal apartments in the evening. The practical machine when run without external resistance that currents, to be reconverted into mechanical force by illustration of the power of the electrical conductor is, on short circuit-heats rapidly, that inefficiency another machine, the question of economy rests in serves to show the possibility of application upon a is shown thereby. On the contrary. should a ma- the perfection of the machines and in their relative large scale, such as I have ventured to suggest. A chine remain comparatively cool when a proper resistances. In respect to the relations that should true comparison between the cost of the electric external resistance is employed, and heat greatly exist between the external and internal work of current and its rival, gas, cannot be instituted until when put on short circuit, these conditions should be dynamo-electric machines, it will be found that the central motor stations are established in populous regarded as an index of its efficiency. As a rule the greatest efficiency will, of course, exist where the districts, where steam power may be produced at internal resistance of dynamo-electric machines is so external work is much greater than the internal the cheap rate of 21lb. of coal per horse-power per low that to replace them by a battery, the latter, to work, and this will be proportionately greater as hour, and whence radial conductors may supply the possess an equal internal resistance, would have to the external resistance is greater. Our measure- neighbourhood within, say, a mile radius, with both be made of very large dimensions, so that the effici- ments gave in one instance the relation of 82 ohm. light and also with mechanical power for minor eney of dynamo electric machines cannot be stated of the are to 49 ohm. of the machine, a condition industrial purposes. The realisation of such s in terms of battery cells as ordinarily constructed. which indicates economy in working. The other system involves the means of subdividing the elec In regard to the second division-viz., the external extreme was found in an instance where the resist. tric current to a certain extent-a problem which work of the macbiae-this may be applied in the ance of the arc was 1.98 ohms., while that of the offers no insuperable difficulties when continuous production of light, heat, electrolysis, magnetism, machine was 460 ohms. a condition indicating currents are used instead of the reversing currents &c. Where it is desired to produce light the external wastefulness of power. which have hitherto been mostly resorted to for street resistance is generally that of an arc formed between lighting. It is well known that in order to produce two carbon electrodes; the resistance of the arc is the electric light cheaply it should be effected in as therefore an important factor in determining the efficoncentrated a form as possible, the reason being ciency. To realise the greatest economy the resistance that the light increases in the square ratio of the of the arc should be low, but nevertheless should concurrent producing it. The same reasoning points to the fact that extreme subdivision of the light for domestic purposes must be attended with great loss of effect, which loss is vastly increased if it is attempted to dispense with the electric arc and to subdivide the mere glow of a wire of platinum or iridium or of a stick of carbon traversed by the

stitute the greater gart of the entire circuit resistance. some of our measurements the resistance of the are was surprisingly low, being in one instance 51 ohm., and in another 79 ohm. It was, however, in some instances as high as 3:18 ohms. It may be noted as an interesting fact that, where the greatest current was flowing, the resistance of the arc thereby produced was low. This is undoubtedly due to higher temperature and increased vapourisation from the carbon. In this latter case also the greatest amount of light was produced. The amount of work appearing in the arc, as measured by the number of foot pounds equivalent thereto, is not necessarily an index of the lighting power. In two iastances of measurement, the amount of energy thus appearing in the are was equal, while the light ing powers were proportionately as three to four. This apparent anomaly is explained by considering

THE PROGRESS OF THE ELECTRIC

LIGHT.

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THE utilisation of the electric light is the subject
which, after the war and the depression of
trade, attracts most attention at present. The
Daily News has been "authorised" to state that
Mr. Edison's light is produced by the incandescence
of an alloy of platinum and iridium. The conductor
is not an ordinary coil, but a peculiar arrangement
of the metal whereby in accordance with a new
discovery in connection with radiant energy,' a
much weaker current is made to generate a given
light than if a single spiral was used. By slight
modification in the shape of the conductor, he has
obtained from one cell of a Daniell battery a light
strong enough to read by. A simple adjustable
apparatus attached to each lamp regulates the
amount of electricity it shall draw from the main
current, and makes it entirely independent of the
current as well as of all other lamps in the circuit.

current.

On Friday and Saturday a portion of the Embank ment was illuminated by Jablochkoff candles, and on Saturday evening the electric light was experi mentally tried upon Holborn-viaduct. The system used was the Jablochkoff, and the machine was driven by a 20 horse-power engine. The light was remarkably steady and brilliant, and about onefourth of the lamps used in the ordinary way were required. The trial, it is understood, will be continued for some time, and arrangements are being made to light the Royal Exchange and the

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