simple as some people are. However, I found a
statement the other day that cost of electric light-
ing was about one-third more than gas, and consider
ing the destructiveness, &c., of the latter, it might
be considered equal. The figures given were, that a
Board of Trade unit, costing 78. 4d., would light an
8c.p. incandescent lamp for 29 hours, and there
were some more figures, which served only to show
that the writer did not understand his subject.
Surely there must be some mistake-78. 4d. for eight
candles during 29 hours. Why, look at it: a gas-
burner consuming 5c.ft. an hour is supposed
to give 16 candles, and a thousand cubic feet would
give 200 hours. Say it takes 10c.ft. to give an
eight-candle light, and then you have 100 hours as
compared to 29, and that estimate is very unfair to
the gas. Cannot the electric lighting companies do
better than eight candles for twenty-nine hours for
78. 4d. ?-or must I still think that gas is very much
cheaper than the electric light? Cannot some of
your readers give better figures than those I have
quoted? I admit they are not authoritative, but
they were given by some one who evidently
believed in the "economy" of the electric light.
Long ago I arrived at the conclusion that the elec-
tric light, like champagne, must be paid for. I
prefer toast-and-water at the price compared with
champagne, and I have an idea that gas is still
cheaper than electricity. I see that the current is
to be supplied at Birmingham for 8d. per unit.
How does that compare with gas? Incans.

"PHYSICAL" FORCE PHENOMENA.

of San Francisco, an account of an automatic comet[32279.]-You gave recently, from the Examiner finder. Perhaps that appliance might be useful in discovering the means by which Miss Mattie Lee Price accomplishes some remarkable feats of strength, whether "physical" or mysterious in their origin I do not pretend to say; but which are published with some detail (and illustrations) by the veracious chronicle above mentioned. Miss Mattie Lee Price is not yet out of her teens, is described as frail, and does not weigh quite seven stone, and yet she accomplishes feats which would, according to the Examiner, "require the strength of a horse."

The following extracts may be interesting; but they are examples only of the feats performed: A feat that Miss Price performs with comparative ease is lifting three men aggregating some 6001b. in First, one man is placed on the chair, another is seated on his weight, says the New York Herald. lap, and a third placed astraddle of the middle man. The chair is then tilted backwards, thus throwing the entire weight on the chair, and leaving only the toes of the first man touching the floor, while the feet of the others are in the air. Miss Price then applies her open hands to the sides of the chair at a point opposite the seat, and after stroking them for a few seconds, as though feeling for the right spot, she says, mildly "All right," and the 600lb. of humanity are lifted in the air, and sometimes sent sprawling pell-mell on the floor.

although not wanting in daring or penetration, has yet an anchorage ground in sober facts about which there is little dispute. But apart from the circumstance that no such hypothesis as Mr. Fraser's is needed for evolutionary purposes, what is the evidence for it, or what are the facts that even suggest it? It looks very much as if a conjecture was first made, and then the whole scheme was worked out deductively from it-a process which it is hardly necessary to point out is decidedly illegitimate. But although no attempt is made, in the letters at least, to apply any inductive test, it is fortunately possible to do so. It is stated that, owing to the uneven distribution of heated masses in space, gravity must be unequal, also that this inequality must entail a general drift of bodies in a particular direction. Well, that is a thing that can be tested. Are those bodies that we can see drifting in any one direction? The answer to this question is apparently that no such uniformity obtains. If this is not sufficient to dispose of the hypothesis, the instantaneous action of gravity should do so. All those who think that force and energy can be bundled together with advantage or clearness, might ponder on this a moment and try to realise what it means. That the influence we know as gravity knows nothing of time, while a wave of energy sets out on a journey, as it were, and desires a definite time to perform it, ought surely to suggest some fundamental difference. And striking as it is, this is only one of a number of differences as sharp and real. But there is another remark that may be made. Any hypothesis that merely endeavours to account for force in terms of energy while leaving matter out of account altogether, is a tame and uninteresting speculation beside those far bolder ones that endeavour positively to construct matter itself out of the ether in motion. The ideas that the ultimate atom may be a vortex ring, or that matter may be resolved into "ether jets" or Another remarkable trick done with a chair was "wrinkles in space," have, indeed, something Explanation of sketch: A, tank nearly full of given off the stage. I took an ordinary chair, fascinating about them, and it is, of course, very salt water; B, circular tube of either thin placed the seat against my breast, grasped both possible that some such hypothesis may resolve metal or glass; C, thin steel plate or plate-glass sides firmly, and braced myself as though I knew I itself or expand itself into a deeper synthesis fixed to axle D; D, axle running in ball bearings was about to come into collision with a "wild-cat" that will include all we know of matter, force, and on supports EE; EE, supports; FF, hollow locomotive." Miss Price simply applied her thumb energy, and explain it all in a manner alike simple rubber tubing, fixed and extending down each side to one end of the front legs of the chair. In a few and beautiful. But that is a long way off at this of aperture inside of tank to circular hole at lower seconds her hand began to tremble, her thumb occadate. In the mean time, we want a theory, or, at least, a nomenclature that is in harmony with the part of tank; B and C running through FF-FFsionally slipping off. I began to feel that I had to knowledge we have arrived at up to the present moment. Having then just learned to distinguish force and energy, the last thing we ought to desire is that the advantage thus gained should be frittered away for a fancied simplicity. As well might we, having a workshop full of tools put to different uses, insist on calling them all spades for the sake of simplicity. We don't get any real simplicity, but we do get confusion. W. J. R.

THE COST OF ELECTRIC LIGHTING. [32276.]-THIS, especially to those who have to pay for it, is a very interesting question, and the electric-light companies, as is only natural, try to make it as pleasing as possible.

The Board of Trade unit, on which the price is based, is light equal to 16 candles for 16 hours, and taking this as a standard, we easily get comparative figures. Taking petroleum, which is acknowledged to be the cheapest light, we are rather hampered for a reliable working standard, as the power of the various lamps in use not only varies greatly for the same consumption, but also the same lamp will vary greatly, depending on the state of the wick and the trimming. We shall, perhaps, not be far out as regards average results, if, taking petroleum at 9d. per gallon, we take the cost per unit of light at 2d. A consumption of five cubic feet per hour of coal-gas in a standard Argand-burner will give us in London a light of between 16 and 17 candles, and this, calculated at 2s. 3d. per 1,000, the present price in the South Metropolitan district, gives us 24d. per unit.

This is very little over the cost of petroleum, and where inferior lamps are used it will, in many cases, come out less, and the superior economy of petroleum in practice is owing to the fact that the lamps are used on a table close to where the light is required, and the general illumination of the room is ignored. If the lamps were placed in the same position as gas-lights are, a far greater power would be necessary, as the available light decreases with the square of the distance between the burner and the object to be lighted.

It may be taken as a rule that one penny per unit for electric light is equivalent to 1s. per 1,000 cubic feet for gas, and when we hear that the charges for electric light are 6d. to Sd. per unit = 68. to Ss. per 1,000c.ft. for gas for the same light, we may safely take it that, except as a luxury, the electric light, although it may be called the light of the future, is not likely to be the light of the present for ordinary use.

Thos. Fletcher, F.C.S.

(32277.)-I HAVE not been very successful in getting an answer to my question on p. 58 as to the cost of electric lighting, because I suspect readers of the ENGLISH MECHANIC are not so beautifully

A STATIONARY WATER-MOTOR. sketch of an idea of mine of a water-motor, in [32278.]-INCLOSED I beg to hand you a rough which the water is stationary. I have not been able to put it to a practical test, and should, therefore, like to have the criticism of your readers as to the friction to be overcome; also the amount of waste water likely to take place, &c.

ལ

I saw Miss Price hold the chair at arms'-length, placing her open hands under the seat. Two strong men were given the most available positions above the chair, and she resisted their combined efforts to force it down. Then, placing her hands on top of the seat, she pushed the chair down despite the two men's efforts to prevent her.

E

A

E

not shown (other side of wheel); G, one of four
thin partitions in tube B.

The steel plate C and tube B are well oiled (if
glass is used, no oil is required), and the hollow
rubber tubing FF is so adjusted as to prevent
water escaping with the minimum of friction and
resistance. The left side of the wheel has an up-
ward tendency, given by the floating power of the
salt water, while the right side of the wheel has a
downward tendency, due to gravitation, so that a
rotary motion is given to the wheel, providing it is
large enough (as the larger the wheel is, the greater
the leverage obtained without the resistance in-
creasing in the same proportion) to overcome the
resistance and friction offered by the rubber tubing
FF.

Perhaps one of your readers may be disposed to make a model (glass would be the best).

V. A. Wraight.

do with a redoubtable opponent, and applied all my strength; but, despite my efforts, I felt myself being pushed backwards by that single thumb. When she suddenly took it off the chair I pitched forward. I weigh twice as much as she does.

While performing in Philadelphia some time ago Miss Price had pitted against her "Fatty" Langtry, the pugilist, who is a member of the Quaker City Athletic Club, and weighs 3081b. It was ludicrous to see this Hercules who could have lifted the girl in the air with one hand fail in his efforts to push her off one foot. Miss Price afterwards placed one hand in "Fatty's" two hands, and dragged or pushed him all over the stage until he cried "Hold, enough!" and retired, discomfited and perspiring, amid the laughter of the audience.

A stick in the hands of a woman is always a thing to be dreaded. Miss Price has a stick about 5ft. long with which I saw her master six strong men

in a very peculiar manner. With this stick she does with six men what Lulu Hurst could not

PETROLEUM BURNER.

orifice.

Rushlight.

job that the lathe cannot be blamed for some of my [32282.]-A is the pulveriser, B mixing chamber, failures. The great merit is the driving-gear: one always do with one. She places it horizontally; C burner, D steam, and E petroleum passage, which can run much slower and much faster than on an three men on each side grasp it firmly, and are must have cocks for regulating the supply of steam ordinary treadle-lathe, and with less fatigue. The She applies her open hand to one end of the stick, drawings. By unscrewing H the steam passes through at times very useful in sliding. How is one to and in a few seconds the six men and the stick are the cone F. When the cock E is opened, the measure a taper? I can't make one really fit the jostled about in a lively fashion, and so shaken up petroleum flows into the annular spaces a, through that the men are soon glad to desist and retire the four holes bb, into the annular spaces cc. By shaking their heads and smiling blandly. She also handled six men in a similar manner by simply unscrewing G, the central passage d is opened, and holding their hands. the petroleum flows into the mixing chamber. G has got a small hole bored through the centre e, by which air flows to the petroleum, to be mixed with it by the rush of steam when the cone F is which the pulveriser is screwed, has got a disc, Y, opened. The cover T of the mixing chamber, into which turns round on a neck on the cover. This disc and the cover have a circle of corresponding holes, kk, bored round the shoulder of the disc. By turning the disc Y the holes can be closed to regulate the quantity of air flowing into the mixing

She afterwards placed the stick perpendicularly and let one man grasp the upper end and another take a firm hold of it at a point about level with his breast. She then placed her open hand longitudinally at the lower end of the stick, and told the men to press it to the floor if they could. Although I have seen this attempted three times by different men, I have never seen it accomplished. The stick will be forced down until her hand comes in contact with those of the man next to her, but no farther. I have investigated this feat so minutely that I am absolutely certain it is not accomplished by means of trickery or confederates.

It is a strange fact that Miss Price performs all these things without any apparent exertion. She says she does not tax her physical strength in the least that she does not have to use any. And, indeed, she does not seem to have much to use. If the above statements are facts, how are they

accounted for?

Dubitans.

PHOTO-MICROGRAPHY OF DRY
MOUNTED TESTS.

chamber.

in Leeds. He is the only maker of them.
Bray's petroleum burners are made by Mr. Bray

J. Brown.

THE CAUSE OF RECOIL. [32283.]-IN a reply under the head of Explosion (p. 187), "Coral" says, " Of course you know the recoil is caused by the rush of air into the barrel after the explosion." If I remember correctly, some years ago it was stated in these columns that the report was due to the inrush of air after the explosion; but I do not think that either statement is correct. Action and reaction in the case of a 132280.1-Ir would be of some interest to learn shot being propelled from a gun are equal, and the why the Podura series of tests have not since the recoil is due to the resistance offered by the gun to date of Drs. Maddox and Woodward's photos been the explosive force of the powder propelling the attempted by photo-micrographers that these shot-not to the inrush of air, which, by the way, pictures, now so old as to be by some considered cannot "rush" in until the gases left behind the shot landmarks of ancient microscopical history, are the are condensed. Perhaps some of your readers can finest we yet possess of this object is certain. It tell us whether or not the recoil commences as soon may be admitted that this class of objects are not as the shot begins to move, or whether it occurs only calculated to test the qualities of a lens depending after the shot has left the mouth of the gun. Is the upon high N.A., yet it seems clear that the reduced shot supposed to drag the gun with it, or does it not aperture utilised, carried as far as possible by cover rather form the movable abutment in a link, the contact with the scale, would yield results superior gun itself forming the real abutment on which the to those secured so long ago. Fine as they were, I thrust is received? If the inrush of air causes the never yet saw one realising the visual image as recoil, what pressure can it have, seeing that the seen in the microscope. We have fine examples gases must be condensed before it can rush in? The of diatoms, and a large series of bacteria, but no argument must be the same whether it is a 100-ton photos of any importance of scale, which, if worked or a mere rifle, and what pressure could any at, might teach some useful lessons in photo-inrush of air exert to give the kick of a rifle? micrography, and add further testimony to the high position of this branch of microscopy. Collorabola.

HOT-AIR ENGINE.

Perhaps some readers can explain: for at present
I do not see the" of course" of "Coral," nor can I
admit that the sound is due to the inrush of air.
Whence is the origin of these statements, which are
often made as if they were established truths?

THE BARNES LATHE.

H.

[32281.]-YOUR correspondent "Video," No. 73919 in Replies to Queries last week, seems to be in the same difficulty as many of us. We have looked up back numbers, and fail to find the construction [32284.]—THE criticisms are mostly just. A top of the pretty hot-air engine, and I feel sure if some slide would be a great addition; indeed, I intend kind subscriber would give drawings for making to fit one. The taper-turning by shifting back same in your valuable paper the same as the steam headstock is a troublesome plan. The tool-holder model locomotive, many hundreds, I think, would is generally convenient, and, besides, it is quite be very thankful.' Being more simple in construc-easy to rig another. The 41 which I have is not so tion than the steam-engine, therefore amateurs and heavy a lathe as an English 34, and has no grip, friends would be pleased to see it. and is really suited for but very light work, though Metallurgic. the man that fitted my scroll chuck made so poor a

HARVARD PHOTOMETRY. Vols. XIV. and XXIV. of the Annals, I felt that I [32285.1-WHEN I became possessed of the two had at last got hold of a star catalogue whose magnitudes might, from the methods of determina magnitudes. Fancy my surprise when I was intion employed, be fairly considered to be standard formed not long ago by a variable-star observer of no mean order, that the Harvard Catalogue was more notable for quantity than quality of the work, that he had measured several of the objects and found a great amount of error in the magnitudes opinion of experienced observers such as Mr. quoted. I should be glad to have the unbiased Knobel, Mr. Sadler, Mr. Espin, or "F.R.A.S.," who have actually compared this catalogue with the stars themselves, as to whether the much-wanted standard measures are, after all, unreliable. Austwick Hall, April 25.

T. R. Clapham.

KAPP'S MULTIPOLAR DYNAMO. [32286.]-REFERRING to your article on the above in last week's issue, the attention of your readers should be directed to the fact that the statement, "that it has hitherto been customary to build up the armature core with complete discs of thin wrought iron," is not correct; and that conse quently the claim for novelty for this form of armature falls to the ground. If your readers will turn to Mr. F. Walker's papers in the "E.M.," nearly eight years ago, on "Practical Dynamo Building for Amateurs (since published in book form by Iliffe and Son), they will see a description and illustrations of an armature built up of seg ments of thin sheet-iron rings, held together br bolts, and two gun-metal wheels, which is almost a counterpart of the one figured in your article of last week.

S. Bottone.

THE WETTEST PLACE IN THE WORLD.

[32287.]-AT the Royal Meteorological Society's meeting on April 15, Mr. Blandford, late meteoro logical reporter to the Indian Government, read a paper on "The Rainfall at Cherra Pongee, in the Khasi Hills of Assam." The records go back to the year 1832, but prior to 1871 they were irregularly kept, many complete years being wanting. There was no evidence that the average fall on any part of the plateau was so high as 600in., though it may have amounted to as much in certain wet years. Frequently between May and September the fall for a single month ranged from 100in. to 200in. In August, 1841, Colonel Sir Henry Yule registered 264in. (22ft.), five successive days in the month, having each of them 30in. of rain. During sever months in 1849-50, Sir Joseph Hooker recorded 500in., also noting one instance of 30in. in twenty. four hours. In July 1865, the total was 203-4 but since 1870 the largest fall in any one month was 184-8in. in June, 1876. For the sake of com

arison it may be stated that London receives on an erage 25in. per annum, and an inch of rain in tenty-four hours is a very rare occurrence. In the Valley of the Brahmapootra, not very far distant from the above humid focality, the rainfall averages 250 to 300in. per annum. In the first year of my sojourn, my new tent was persistently soaked, got mildew, and fell to pieces, so I had to fall back on "hutting," the ever-present sword grass and wild plantain leaves furnishing the materials. On one occasion (about the present date) I was imprisoned for 48 consecutive hours, the liquid element descending in large drops with great force; my kitchen was installed in a similar erection, sending forth the savoury steam of venison steaks and boiled buffalo tongues, while my followers sung, smoked, and talked in like fashion; my pipe and book were my sole recreations during this tedious confinement, and the only means of escape the melted snows of the upper mountains and rainfrom the extensive island were by my elephants, water combined, having raised the main river by several feet. I expect to hear that the forces now marching on to Munnipoor will suffer greatly in health and comfort on their return journey to the great river, as the wet season has already begun, when leeches, mosquitoes, and fevers become the ruling plagues.

CHAIRS AND THEIR NICE

Eos.

LITTLE WAYS-TO "ONE WHO WISHES HE WAS NOWHERE.' 999

[32288.]-SOCIALIST chairs, boots, and coats are unquestionably most desirable if they are all as durable as your own; but Socialism in its theoretical aspect is, it is to be feared, a mere chimera. Just for a wee while the Church of Christ was Socialistic, and was apparently meant so to continue. I need not say that it has so degenerated that hardly a trace remains of its old characteristics.

I sympathise with Socialism, but not with the rough side of it, which is the side too generally offered to view. It never will be an accomplished fact until the Millennium introduces it. Brute 1 force can never thrust it upon mankind. To me, it is simply horrible to think of the waste and luxury and apathy of the Upper Ten, and of the hopeless, helpless misery which the superfluity of the first named could entirely relieve. Yet I also feel that if all the money of the wealthy could be collected into one vast heap, and all the wealth of the world added to it, and if this could be simply divided as if all had a common purse, a single century would suffice to reintroduce the evil. The race would begin again; competition would make itself felt as heretofore; the idle and unprincipled would prey upon the industrious, the far-sighted and keen men of business would make their pile, and it would not be so long before we again had experience of " Chairs and their Nice Little Ways."

O. J. L.

Chippendale, 40s. or so. For equal strength the
Chippendale will be near twice the weight. Both
may be admirable in their place and at their price,
but it is well to understand the distinction. I have
so long tried to design diagonal trussed work, and
so persistently failed, and observed others to fail to
produce shapely results, that at last I began to sus-
pect that there must be something wrong about the
theory, and believe that this is the true account of
the matter.
Rushlight.

SHIP'S LIGHTS.

[32290.]-A CURIOUS optical phenomenon was brought under my notice last summer by the captain of an Atlantic liner. It consisted in the different intensity of the rays from the ship's lights as reflected back by the fog as we steamed through it. The green light reflection was most intense, then the port side; indeed, unless the fog were very the white from the mast-head, then the red from thick, this latter would not be perceptible. The mast-head light, being an oil lamp, was more yellow than white, and so we may say that the reflection intensity, or, perhaps as may be, the penetrating power of the reflected rays, was inversely as the wave length. In the case of the sun in a fog, we know that it is mostly the red rays that push through, those of a higher refrangibility being absorbed. These observations were made from a point whence the direct light of the lanterns was completely shielded. I should be glad to have the explanation of this phenomenon from some one of your readers.

REPLIES TO QUERIES.

fully requested to mention, in each instance, the title In their answers, Correspondents are respectand number of the query asked.

add an extra manual with two rows of reeds to [73861.]-American Organ. -Mr. P. Rice can his harmonium with very good effect. If he will send me his address, I will give him a drawing of a most successful plan. American harmonium reeds can be bought for Ss. 6d. per set of five octaves. and can be made to speak well with a light presThese are similar to those used in American organs, sure of wind, and can be voiced more easily than the ordinary harmonium reeds. A manual coupler can also be addel, and an octave coupler, without manuals and pedals can be placed in a proper posimuch trouble. If pedals are required, it is better to have one made specially for pedals, so that the tion for comfortable organ-pedal practice.

Stubbins, near Manchester. J. SCHOFIELD. [73861.]-American Organ.-Harmonium.— There is no difficulty in adding another pan to an existing harmonium, and another keyboard, if the "adder" does not mind pulling the case to pieces at the top. As to whether it is better to put the additional pan vertical or horizontal depends on other arrangements for instance, whether the keys are of the balanced type or hinged at their heels as usual. It would be much better to build such an instrument than to attempt to alter an existing one. American organ reeds can be used with a pressure bellows, but not to any good purpose. They are adapted to their own environments [32291.]-IN the Queries I note a question as to-not to the conditions existing in an harmonium. the power required to heat 850 gallons of water 20° As I have refused to assist "Gimal" in spoiling his Celsius, which is equal to 36 Fahrenheit. The Alexandre harmonium, I ought not to criticise Mr. matter is one little understood by most people, and Slatter's device; but I may say that I retain my domestic questions, an extended answer may be of instrument as it is. as it is closely connected with many commercial and opinion still, that "Gimal" had better leave his ORGANON. service.

WATER-HEATING.

M.

The British standard unit of heat is the amount
necessary to raise 1lb. of water 1° Fahr., and one
gallon of water weighs 101b. Multiply 850 gallons
by 10, the pounds per gallon, and again by 36, the
number of degrees F., the temperature required to
be raised, we get 850 x 10 x 36 =
of heat required to do the work. The average
306,000, the units
heating power (theoretical) of good coal is about
13,000 units-i.e., 1lb. of coal should, if all the heat
were utilised, heat thirteen thousand times its weight
of water 1° Fahr. All the heat is not utilised in
practice, and we may expect to get, perhaps, 8,000
units per pound in ordinary working. An average
good boiler without forced draught will burn about
lb. of coal per hour per square foot of grate sur-
face, and thus 71b. x 8,000 units gives us 56,000
units of heat per square foot of grate surface.
Dividing 306,000, the required units of heat, by
this 56,000, we get nearly 54sq.ft. of grate surface
required in the boiler, which means also a boiler
having at least an available heating surface of
55sq.ft. Seven pounds of coal burnt on each of the
5sq.ft. of grate surface gives 384lb., the coal re-
quired to do the work with a first-class boiler.

To do this work in one hour without previous
preparation, which is what I understand your
correspondent requires, is anything but a simple
matter, and would require a special boiler of a
power far exceeding the above, which, of course,
only deals with the boiler in its state of maximum
efficiency in steady, full work.

[32289.]-I Too read "O. J. L.'s" notes with great pleasure, and I too have bought rush-bottomed chairs of the poet-artist and socialist, and I know some of the 10s. 6d. variety that have been in use over 20 years, and I find that most artists and their friends failing to procure old Chippendale, or unable to pay 40s. or 50s. for new Chippendale, do buy rushbottom chairs. The names "Early English furniture" and "Art-furniture are advertising nonsense. If they mean anything, it is that the things are bad copies of the work of such master designers as William Morris and Philip Webb. The design or the workmanship of furniture may be good or bad; colour may be natural or artificial, but art-work" andart-colour" are just bad English. I fear I must differ, albeit with much diffidence, from "O.J.L." in the matter of diagonal bracing. I don't think the disuse of it in furniture is a mere question of fashion; there are structural principles involved. Even in bridge engineering we arrive at a point at which the simple plank is better than the lattice girder, and similarly I am strongly inclined to believe that the whole province of joinery, in-culty in the fact that coal-gas, simple and econocluding cabinet-making is out of the range of the diagonal truss.

One point that has, I think, escaped the notice of writers on the theory of woodwork design is that, apart from heavy carpentry, there are two fairly distinct groups of woodwork-on the one side joinery, wherein strength is secured by accurate fitting of the square shoulder and the tenon; on the ether a somewhat miscellaneous group, including the work of coopers and cartwrights, ladder-making, and turning, which, for the most part, eschew the square shoulder.

You will see at once that chair-making falls into two distinct trades, which we may dub respectively the Chippendale and the High Wycombe. The first is joinery, the second is of the ladder class, and is, I Submit, the proper system when both strength and lightness in a high degree are required. Crossbracing clearly would not improve a ladder, and I don't see how it could be applied to a chair with advantage. The High Wycombe chair can be made to sell at from, say, five shillings in perfection; the

The costliness of coal-gas on so large a scale would probably prevent its use, notwithstanding the fact that, with this fuel, water-heaters are made which attain their maximum efficiency in a few seconds after the gas is lighted. As a matter of practice, 20c.ft. of average coal-gas will do the work of 1lb. of the best coal when the latter is used under the most favourable conditions possible, and therefore 38 × 20 = 770, the number of cubic feet of coal-gas required to do the same work.

We are here again confronted with a serious diffimical as it is on a small scale, is difficult to deal with in large quantities, and a consumption so large as 770c.ft. per hour would require a supply of air under pressure to enable it to be satisfactorily burnt. The matter practically resolves itself into this: that to heat the water required in one hour, without preparation, a boiler would be required with 10sq ft. of grate surface, 100sq.ft. heating surface, and an experienced fireman to get the fire quickly at its best. Thos. Fletcher, F.C.S.

A DESIGN for photographic studios, by means of which the glass roof is dispensed with, has been tried by Herr Eggenneiler. Herr Eggenneiler's studio is a room facing north, with an ordinary solid roof, which slopes to the south, while the northern wall, or side, alone is built of glass, and is of about twice the height of the southern wall. The roof is painted white, and a reflector or "light distributor" is introduced to equalise the top light.

Harmonium.-I should advise Mr. Rice to make
[73861.J-American Organ. Addition to
his upper manual entirely on the American-organ
principle. There were some instruments exhibited
ferent instruments in one case.
at the Inventions Exhibition containing two dif-
The lower manual
manual on the American-organ principle. Could
was on the harmonium principle, and the upper
be played either separate or in combination, and
the change from one manual to the other had a
marked and pleasing effect. As Mr. Rice intends
adding two sets of reeds to the upper reed-pan
(which must be placed horizontal, not vertical), he
instead of enlarging the bellows, I should advise
will find the present wind supply insufficient; but
him to widen the case at the back 12in. or 14in. Get
the vertical-acting type, cavity board, reeds, and
an American-organ exhaust bellows and reservoir of
keyboard (C scale), place the whole system in the
case at required height for the keyboard to be at a
suitable elevation for an upper manual. Connect
the blow-treadles to both sets of bellows if to be
blown by the player, but to the blow-lever if other-
wise. All the fittings are cheaper to buy than to
this case, which is the manual coupling, owing to
make. One difficulty, however, presents itself in
the stop-work over the lower manual: unless the
stops can be arranged on each side to connect one
manual to the other will be difficult. Independent
pedal-action can be fitted to either harmonium,
organ, or piano.

W. SLATTER.

[73861.]-American Organ. Addition to Harmonium.-The reply of Mr. Slatter (p. 183) is scarcely satisfactory. The "simple manner of adding the half-set of reeds may be easily understood by a look at the sketch (p. 143)." But there is also something else very simple to be discovered there. Mr. Slatter says that "no blocks will be required"-in the additional channels for the 4ft. half-set, and that both (the 16ft. and the 4ft.) "communicate through the same channels." But he does not answer another and very pertinent question I put on p. 162: "Are there any blocks in the channels of the row over which the 4ft. is to be fitted?" If this harmonium, to which the halfset of 4ft. reeds is to be added, is one of Alexandre's, the probability is that the channels are cut out of the solid; but whether that is so, or the pan is one of the built-up kind, it is certain that the channels are not all of the same length-that the channel for the mid. F is much longer than the channel for the top C. In fact, for top C, whether the channel is cut out of the solid or is built up with partitions and blocked off, the pallet aperture and the reed aperture will overlap, and the channel will not be much longer than the reed itself. How, then, can Mr. Slatter's top C of the added 4ft. speak into the channel of the top C of the 16ft.? Whether a pan is cut out of the solid or built up, the channels diminish in length from the first octave upwards until, in the 8ft., there is practically only sufficient length for the top reed, and the depth is reduced at the same time, so that the pallet veneer and the reed veneer meet in the 8ft., and "all but" in the 16ft. Possibly Mr. Slatter has some method of

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1362.

overcoming this difficulty-easy enough if the
instrument is built on the plan of his half-set of
4ft. "addition," but rather difficult in the case of a
harmonium built as it should be. Even if the

channels could be made to communicate in some
way (I confess I cannot see how), the 16ft. would
certainly speak before the 4ft., if the latter spoke
at all, and what 4ft. reeds would be like on
channels all of the same length I do not know.
need not ask whether Mr. Slatter has ever adapted
I
such an arrangement to an Alexandre or any other
harmonium; but I might suggest to him that in
the back volumes he will find illustrations of
harmonium pans, and he can learn from them that
the depth, as well as the length, of the channels
varies, decreasing in both cases as the upper
octaves are reached.
might answer for a Seraphine or a German con-
Mr. Slatter's arrangement
certina; but not for a harmonium, and the mere
attempt to add such a thing to an Alexandre would
be an act of folly on the part of any one who
really understood how a harmonium is built-in
fact, he would not attempt it.

G. F. B.

been issued with "remarks" by those competent to
express an opinion.
require adjusting. You can only be told how to
[74034.]-Telephone.-Perhaps your instruments
NUN. DOR.
the by screwing up the magnet, or testing
not; a job like this cannot be put to rights by
whether the wires in telephone are continuous or
these instruments-as, for instance, you might have
writing, on account of the funny eccentricities of
regulated the distance all right, but somehow or
other a bit of grit has lodged between the magnet
and diaphragm. Who would know this in a closed-
up instrument? Perhaps a sharp knock on the
bottom would set matters right.

Μισκ.

states that the current varies with, or is measured [74055.] - Electrical.-" Hysteresis" correctly of local action). Let him reverse this statement, and say, which is equally correct, that the zinc by, the weight of zinc dissolved (supposing absence dissolved varies with the current, and he will see that Mr. Bottone was not in error, since resistance and current are related. All these questions can be solved by Ohm's law. There are no exceptions.

SM.

MAY 1, 1891.

1.169

[74150.]-Electric Alarm-Clock.-The illus the ordinary clocks; but I do not think that any the one I described. The defect of that (if defect i trations on p. 185 show some of many ways i contact with its brush is liable to be retarded, and which an electric-alarm can be adapted to any of the one of them is better (certainly not simpler), than may, therefore, if very tight on its arbor, stop the clock. I do not think it at all likely to occur; buteed up it can be called) is, that the hour-hand making the difficulty (if it exists) has been solved by the addition of another hour-hand, which can be shifted about where you please, and still leave the clocksons fitted up such an arrangement as I described clock-dial, and carry the contact-brush. One of my hands indicating more or less correct time. The additional hand may be coloured to match the some years ago, and it answered excellently.

Ende by used dr rathe

"New Scotch Reader" may use this method to [74150.]-Electric Alarm Clock.-Perhaps NUN. DOE. [73974.]-Quill Pens.-Some little skill is required in making good quills for pens, and practices had it in use every morning for over three years, advantage with his clock, if an alarm one. I have differ, though the trade is now confined to very few There is no doubt that the greater surface of zinc at any hour or minute of day or night, just as any hands. Some place the quills in hot sand (about exposed to the action of the acid does increase the ordinary alarm clock. It is quite simple in action, [74055.]-Electrical.-To "HYSTERESIS.". and has never failed once during that period. It is 210° Fahr.), and then scrape and rub them with a current to a small extent; and this fact has been and sure so long as alarm-spring remains intact. entirely an idea of my own, and can be set to alarm piece of cloth; others steam them for two or three noticed in this paper by Mr. Sprague (1874) and by The face of clock does not require to be disfigured hours, and then stove them in an oven for some myself. But if you will try the following experi- by it, and the work can be done in ten minutes, as hours at a moderate temperature, though. The ment, which was a common school demonstration follows:-Take line and return wires, connect one quills must be "cooked," may be stained, or cleared by dipping in a weak think you will admit that the chief increase in cur- which must be uninsulated; wind up alarm-spring, so to speak, and they when I was at the Collegio del Carmine in Turin, Ito works of clock, the other to gong of alarm, solution of hydrochloric acid. gradually going out of use, except in places where internal resistance. Take a plate of zinc and a all but clears pellet on striking gong; then attach fads prevail and in Government offices-for inQuill pens are rent in large cells depends on the lowering of the and bend spindle of striker so that escape-wheel stance, the Patent Office Library, where it is diffi- plate of copper, say 2in. wide by 8in. long. Procure a piece of small cord to centre of spindle, and bring cult to find a quill pen with which you can write a cell containing dilute sulphuric acid and a tangent it out in line with the centre of spindle to outplainly. The system will be kept up, although steel solution to the depth of lin.; do likewise with the clock to alarm at time required by moving nibs are much cheaper. galvanometer. Now immerse the zinc plate in the side of clock, taking it over the gong. Set NUN. DOR. (73980.1-Resistance for Arc-Lamp.-Will meter. Now, leaving the zinc plate at the same spindle to bend, and allow one tooth to clear copper plate. Note the deflection on the galvano- alarm index-wheel, then pull cord, which causes does want to know? explain his query, or say what he point, gradually immerse the copper plate 2, 3, 4, 5, pellet, escape-wheel then acting on opposite side of question as it stands, even with the illustration? How can anyone answer his &c., inches, and note the corresponding increase in pellet causes striker to rise clear of gong, and the deflection of the galvanometer. Now lower the breaks the circuit, the wire which travels the 178987.]-Indiarubber.-What does "Tojin" M. T. L. zinc plate. It will be found that a corresponding circumference of index-wheel preventing the striker mean? Sulphuric acid is not used in the "pre-face. Now approach the plates to each other, and striker falls on gong and completes the circuit, rise in current will take place, proving that the in-flying back on gong until it reaches the notch paration" of indiarubber or guttapercha; but note the rapid increase in current, due entirely to which remains completed, as the escape-wheel is crease of current is chiefly due to increase of sur- (which will mean the time adjusted for), then sulphur is used in the vulcanising process. [73991.]-Sectional Area of Steam-Pipe.should be perfectly clean, to insure good contact. T. G. There are many little books published which conprevented from clearing itself by the spindle being tain tables giving the area of pistons, &c., and bent until the cord is pulled, or switch be put to “E. L. P." should refer to one of them, instead of "off." The points where gong and striker touch working out the sum every time he wants infor

"Linesman"

mation of the kind.

C. S.

[73995.]-Brick Ovens.-The querist will find much information in back volumes; but he appears to want something special. An ordinary baker's oven is heated by a furnace at the side, the flames playing freely under the arched roof, which becomes a "scorching top heat," it. When the bread is in, however, the moisture as the querist puts from that rises and damps the "scorching top heat." I suppose the querist understands that the fire is withdrawn before the bread is put into the build suitable ovens; while if the querist is in As a rule, country bricklayers know how to town, he can easily find out those who build the ovens for the regular bakers.

oven.

T. M. P.

[73996.] Graphic Statics. "E. A. A.'s" reply (p. 184) and to mine (p. 142), Referring to the magnitude of the greatest bending moment is not determined from the shearing-force diagram, but only the position of it, which is at the point (P) where the shearing-force changes sign. J. S. C.

[73998.]-Indicator.-Put a light eccentric on the shaft and make the free end operate a counting wheel by means of a pawl. If high numbers are wanted, use an index like that seen on gas-meters. The "speed" can easily be read by comparing with a clock or a watch. R.

decreased resistance.

would do wisely to try and find out if the spherical
aberration in his object-glass is due to the centre
[74089.]-Astro. Object-Glass.-" Amateur
S. BOTTONE.
rays being too long or too short; if too long and the
back slightly convex, I am doubtful of any remedy
crown glass is unequal convexities and flint glass
short, turn the crown or convex lens over, or the
only by regrinding.
other side in front, which will no doubt improve
But if centre rays are too
definition with full aperture.

G. W. HOUGHTON.

wire through each core, the size of the hole in pro-
his cores?-i.e., he should make a hole with a vent
[74118.]-Core Sand.-Does "Beginner" vent
portion to the size of the core.

W.S.

whatever to do with refraction in any shape or query, as "La Lune" now puts it, has nothing [74120.]-Atmospheric Refraction. This form. The apparent enlargement of the sun or moon when seen near the horizon is simply an illuvery simple experiment will even suffice to show by proper instrumental means at once corrects. A sion of the judgment, which actual measurement this. If a momentary glance be directed towards the sun (when not too brilliant), a spectral image is immediately imprinted on the retina of the eye, and it will be found that this image seems larger in which persists for some considerable time, and may the latter case to the same extent as the actual disc be readily shifted at will from zenith to horizon; of the sun when so observed. Several years ago this subject was discussed at some length in these columns. Opinions do not seem fully agreed as to John Herschel in his "Outlines of Astronomy" the cause of the illusion; but the view taken by Sir appears to offer the most satisfactory explanation of the matter-viz., that when near the horizon, we terrestrial objects that may be interposed or placed view and judge of these bodies as we do of in close comparison with them; in detail, and with than overrate their apparent magnitudes. The an acquired habit of attention to parts aloft, we have no associations to guide us, and their insulation in the expanse of sky leads us rather to undervalue illusion is not, however, confined to celestial objects. [74004.]-Jet Propellers.-I do not think there on a level with the eye, and it is sometimes difficult Objects generally at a considerable elevation appear are any reliable data. to be smaller than when placed at the same distance upon as failures, and no definite data have ever been same, and even when the actual size of such objects Jet propellers are looked to believe that their angular measurement is the obtained by any of the recognised authorities. A is known, one can hardly divest one's self of the paper on the subject was read last September by idea that they appear different. I have frequently Mr. John Ruthven before the Institute of Marine noticed this on comparing the apparent heights and Engineers, which can be obtained no doubt by sizes of persons on the top of the Monument with addressing the secretary at Langthorne Rooms, those on the ground, making due allowance, of Stratford, E. Mr. Ruthven knows as much about course, for the effect of foreshortening in the the subject as anyone, and the paper referred to has former case.

[74002.]-Cutting Square Threads.-Cannot well be done with stocks and dies; better cut it in a lathe; but as the casting is so heavy, you might try a milling tool, and take that to the work. easy to advise as to best way without seeing the It is not work and learning exactly what has to be done. [74003.]-Charging Leyden Jar.-"Student W. R. should try whether "close" or in actual contact will charge his Leyden jar most effectually. I suspect he will find it does not make any difference. E. M. F.

W. T. N.

cores are not suited to a machine with H armature. plates screwed to pole-pieces, or cast in one with [74154 and 74294.]-20c.p. Dynamos.-Circular this latter. The following proportions will make Use flat cores: they can be either wrought-iron an efficient machine:-F.M. cores 5 by 4 by fin.; at 45 volts pressure if driven at 2,500 revs. per min. No. 20 d.c.c. This machine will give about 4 amp. 22 wire B.W.G., d.c.c., and the armature with 10oz. armature, which must be laminated, not cast, 4 by 1in. The F.M.'s are to be wound with 44lb. of No. Bisect A B and draw perpendicular a C; bisect BC exceedingly well. I have made several to above sizes, which work and draw perpendicular e A; bisect CA and draw [74195.]-Problem. - Draw triangle ABC. F. ASKEW. perpendicular ƒ B. The centre of each circle will b

No