HE passenger elevators at the Chicago audi-
im are designed to travel at the rate of 600ft.
minute. The length of the lift is 220ft.
bollar Sign. The dollar sign, says an American
er, is not a monogram of "U.S.," but dates
a the days when the transfer was made from
nish to American dollars, and accounts were
t equally in dollars and reals. Thus: one
ar eight reals (American and Spanish parallel
Junts). Later the 8 was placed between the
cellation mark, 18]; then the perpendicular lines
sed the S, and finally the 8 shaded into an S,
, combined with the cancellation line, evolved
present sign ($).

entists' Moulding Wax.-Dr. Davis com

icates to the Journal de Pharmacie et de mie an analysis of the composition known as F-odiva " or "Stent." Upon this he bases the owing formula: Stearin, 25 parts; half-soft al, 25 parts; talc, 50 parts; carmine, 0-5 parts; of rose geranium, 2 drops to the ounce. Melt resin by the heat of a sand-bath, and when htly cooled add the stearin, stirring constantly. en this has melted add the other ingredients, viously intimately mixed, and stir so that a 1ogeneous product may be obtained. The adheness of the composition may be increased or inished by modification of the amount of copal. more thorough blending of the colour may be red by dissolving the carmine in a little potash ation before mixing with the chalk.

oftening Water.-For softening water by ans of hydrated oxide of lead cheaply, it is essary to obtain the oxide, and the following thod has been devised by M. Villon. A solution jodium nitrate is placed in a vat, divided into compartments by a diaphragm; lead electrodes large surface are placed in the solution, and the rent from a dynamo then passed through. The ium nitrate is decomposed, caustic soda being med in the negative compartment and nitric d at the positive pole from which it disves a certain quantity of lead, forming lead rate. When the current has passed through liquid for a certain time, the solutions are run m the two compartments into a second vat, d there mixed by means of an agitator. The la precipitates hydrated oxide of lead and itself rms sodium nitrate; the solution is then filtered d the nitrate solution again submitted to eleclysis. When the baryta or lead oxide are used , they are replaced by freshly prepared oxides. e purification by barytes is more perfect than at by lead oxide. According to M. Villon, the e of the filter press can be avoided by employing umbate of sodium-a solution of lead oxide in ustic soda. The precipitate is simply allowed to ttle out, and the water obtained shows a hardness E about two or three degrees.

[73371.J-Slow-Combustion Stove.-I cannot agree with "Nun. Dor.," p. 550, that these are all stuff. I have one by me as I write, which comfortably warms a place only occasionally in use, and does so for six hours on a filling with the cinders from the house fires and a little coke breeze. Surely this is very useful. Of course, they have the defect, inherent in all stoves, of making the air unpleasant-not by any escape of fumes, which I have carefully seen to, as I got it to see if it would do for occasional use in a greenhouse, but probably by charring dust particles and over-drying the air.

SIGMA.

[73494.] Rapidly Rotating Cylinder."C. Q. T." is perfectly correct about the centrifugal force, as I find on looking at my calculations I have made a mistake. But to run a steel disc so as to give it a strain of 67,700lb. per sq.in. is, in my opinion, dangerous-from 25,000 to 30,000lb. is as high as I should like to run one. Regarding the belt velocity, I still think 6,000 ft. to be as much as you will be able to obtain. The belt above this speed on so small a pulley will not grip sufficiently to drive. I suppose you intend to drive the shaft from some engine, as the size of pulleys necessary to drive it by hand would be prohibitory. The statement which you have quoted from “Unwin” has reference to large driving drums, and will not apply to such small work as you require. As regards the best bearings for the spindle, I should advise bearings of white metal, having good oil-grooves cut in them, with oil-cups to give a continuous stream of oil while running, and use either castor or olive oil-thin oil certainly will not do. I have had no experience of small work running between jewels; but I should think it would be very unlikely to succeed; certainly, it would not be able to be run without lubrication. But if you could run it for a minute at this speed with lubrication, you could run it for an hour, if necessary, for, if it will not heat in that time, it will run any length of time without heating.

SPHINX.

[73469.]-Remelting Scrap Zinc.-I do not know of any book specially devoted to remelting scrap zinc; but if the querist wants to melt zinc, whether scrap or spelter itself, he has only to provide himself with a furnace capable of getting up a temperature of, say, 800° Fahr., a crucible, and some salammoniac to prevent the zinc being oxidised when melted, to treat any quantity of scrap zinc by instalments. T. C. L.

[73476.]-Defective Injector.-Send the particulars to the makers and ask their opinion. No one can give much useful information without examining the injector. Apparently there is too much water, as it works better when water is partially turned off; but it is no use guessing. Ask the makers, or get some expert to examine it.

NUN. DOR.

[73481.]-L. and N.W. Bloomer Engines.These have been given over and over again in back volumes, and photos. of them can be obtained from the dealers in such things. Look through the indices if you want such a thing. CREWE.

[73482.]-Phonograph.-The producing stylus has a chisel point; the reproducing a round knob. Sperm wax is utterly useless: it must be something much harder. At least, Edison uses a cylinder which is a compo of something about as hard as plaster of Paris.

NUN. DOR.

[73486.]-Oil Engine.-This querist asks for something which no one has yet invented. There are oil-engines in the market, but none so small as one-man power. Better have a hot-air engine.

PATENT.

173509.]-Electric Light Shunt Dynamo.— Quite so: electricity is but a form of energy. It will, therefore, tend to clearness if, for the future, in speaking of electro-deposition or incandescent[73432.]-Surface Condensers. I do not lamp lighting, we discard all the intermediary words, know by what means the tubes in the condensers of and say at once that it requires 33,000ft.lb. to any given ship are made tight, but there is no deposit so much copper or give so much light. The difficulty in doing it, and not much tightness re- table given by "J. W. W. B." in last week's issue quired. The general plan is to pack each tube is not nearly so full as the one I gave about a year separately, making a screwed stuffing-box in the ago, when treating on incandescent-lamp lighting, tube-plate, when a screwed ferrule and tape pack-to prove that ordinary lamps take about 3.5 watts ing prevent all leakage of sea-water into the feed; per candle-power. but of course the tubes must be examined from time to time. Perhaps some correspondent knows exactly how the tubes of the Teutonic's condenser are kept tight.

66

work done.

M. E.

M. T.

S. BOTTONE. [73644.]-Strength of Field.-If iron could never be saturated with magnetism, then "Slow Speed" would be perfectly correct in his idea that by doubling the magnetising power he would double [73439.]-Manufacture of China.-Depends the E.M.F. at the same speed of running; or, as he on the quality of the goods, whether moulded or requires it, get the same E.M.F. at half the speed; turned. Common stuff is often moulded, but the but on account of wrought iron becoming saturated practice varies at different potteries. The term is when about 150,000 lines per sq.in. are forced "thrown," which includes moulding and turning-through it, he would not do so. I have not calcumoulding in the sense used by the querist meaning lated out the number of lines passing through the casting," ," which is often used for the best work. armature core in "Slow Speed's" machine; but if it The "few hints" asked for would be occupying is a good machine at present, there ought to be space to no useful purpose. Querist should see the about 120,000 lines per square inch of section in the armature core. Now, as I said before, 150,000 lines is about saturation point; so however much you may run up your exciting force, you cannot force much more than this number through, and as the E.M.F. of any dynamo depends first on the speed, second on the number of conductors counted round the armature, and third on the number of lines of magnetism passing through the armature [73448.]-Arc Lamp.-A hand-regulating arc core per square inch of section, you can easily see lamp is out of date, nowadays. Querist had better that it would not double the E.M.F. of your read up the subject, and make any of the well-machine. As a matter of fact, the magnetising known forms if he is not quite clear as to what he force, when the magnet is near saturation, increases wishes to do. VOLTOHM. out of all proportion to the amount of magnetism forced through the cores. If there is a large amount of iron in your dynamo, it will increase the E.M.F. undoubtedly. If the piping connecting your engine and boiler is rather small, the slower speed will benefit, as you will not lose so much pressure between engine and boiler, but not otherwise.

[73443.] · Field Magnet Winding of Dynamos.-"J. W. W. B." is quite correct, especially about the diagram of the specially wound shunt dynamo, to which no reference had been made by me in my replies; and about Ohm's law.

S. BOTTONE.

Barometer Plants.-A French meteorological
aper contains a list of prognostics apropos of the
spect that certain plants present according to the
cates of the atmosphere. The following are a few
xamples:-If the head of the gith (Nigella sativa)
roops, it will be warm; if the head of the same
lant stands upright, it will be cool. (The gith in
his country is usually Agrostemma githago of Lin-
eus-the corn-cockle.) If the stalks of clover and
ther leguminous plants stand upright, there will
De rain; if the leaf of the wood-sorrel turns up, it
s a sign of a storm; if the leaf of the whitlow grass
lowly bends up, there will be a storm; if the
lower of the convolvulus closes, it will rain;
f the flower of the pimpernel closes, it
will rain; if the flower of the hibiscus [73449.] Electrical Resistance.-"A. R."
seems to want something not yet discovered; but
doses, it will rain; if the flower of the sorrel opens, he will find the latter part of his query answered in
t will be fine weather; if the flower of the same
plant closes, it will rain; if the flowers of the
arline thistle close, there will be a storm; if the
ower of the lettuce expands, it will rain; if the
Tower of the small bind-weed closes, look out for
ain; if the flower of the pitcher plant turns upside
own, it will rain; but if it stands erect, it will be
ine weather; if the flower of the cinquefoil
expands, there will be rain; but, if it closes, the
weather will be fair; if the flowers of the African
marigold close, it will rain; if the scales of the
easel became close pressed against each other, it

vill rain.

many back volumes. It depends entirely on how
many plates he wishes to lift which method is
adopted; but there is no difficulty in raising the
plates by turning a roller, or they can be lifted
bodily out of the solution at once by attaching the
zincs to a bar, which can be lifted up. So simple a
matter does not require a sketch.

E. M. F.

SPHINX.

[73664.]-Ventilator.-If A. Gray wishes to cause draughts, he cannot adopt a surer method than "by trusting to the air coming in round the doors and windows for the supply of fresh air." The best fresh-air inlet is some form of the socalled "Tobin" tube, i.e. one which throws the The top need not air in an upward direction. HALL. NUN. DOB. be more than 4ft. above the floor-level.

[73451.] Phonograph. The drawings of Edison's latest phonograph can be found in the specifications of the patent; but "full working drawings" are, I suspect, to be obtained only in the inventor's workshop.

down, the balls fall in, make contact, and ring the bell. In No. 2, the same parts are used, except that a pair of friction pulleys drive the tube G which contains mercury, and this, on being rotated, assumes the parabolic form, and breaks contact with the screw K., which can be lowered to suit any speed. If the puller slows, the mercury becomes level in the tube, and makes contact. I hope one of these may meet your case; but I imagine, if it is to be used with natives in India, the constant ringing of the bell will prove a greater annoyance than the slowing of the punkha. SPHINX.

[73734.]-Mechanical Punt.-Considering the short distance you would require to propel your punt, and the slow rate of speed necessary, I should certainly advise a coil spring with a two-bladed propeller. I have had considerable experience in this line of shooting and propulsion. If you will advertise your address, I will go into detail and communicate with you. DUCK.

[73754.]-Screws.-I cannot understand for the life of me how this querist can cut square threaded screws and nuts to fit, without knowing the use of calipers and depth-gauges. A. MORGAN.

mp

ticles must remain in, depends on the battery
rrent, and the thickness of coating required.
S. BOTTONE.
[73756.] Self-acting Blowpipe. I have
und the best of these is the "Russian blast
"-a vessel resembling a small copper sauce-
an with double sides. The spirit contained in the
ner receptacle is heated from below, when a long,
erce jet of flame is expelled by the vapour. It
procurable from the vendors of chemical
pparatus. I am sorry I have not time to copy the
agram and description from "William's Hand-
ook of Chemical Manipulations," where other
inds are also illustrated.
Eos.
[73758.]-Wimshurst Machine.-The greater
le number of sections, the easier is it to start the
achine; but the shorter are the sparks.

S. BOTTONE.
[73759.]-Electromotor.-To MR. BOTTONE OR
[R. ALLSOP.-Begin by throwing away your brass
obbins. Dress your field-magnet cores with brown
aper glued on, wind them with about 1lb. on each
No. 18 wire. You may put on about 12oz. No.
5 for the armature, and connect up in series with

le brushes.

NUN. DOR.

[73762.]-Grindstone.-Well wash the stone,
in quicker, and keep clean by using more water;
othing else required.
A. MORGAN.

[73768.] Tank. - Multiply the area of the
bottom by the height, which will give cubic feet or
inches, and convert into gallons if required. Thus,
according to your question, a circular tank of 2.5ft.
diam = 2.5 x 3.1415926536 × 5·5 = capacity in
cubic feet (x) x × 6·2321 gallons.
SM.
[73769.]-Dock - Gate.-33ft. of water equals
nearly 15lb. per square inch. To find the pressure;
take half the height of water outside the dock, and
as 33: 15:5: 2.27 pressure per square inch.
Multiply this by the area of the dock-gate exposed
to the water in square inches, and you have the
total pressure on the gate; so 2.27 x 120 x 120
32,6881b. If the water were only half the
height, or 5ft., it would, of course, be half this, or
16,344lb.

=

SPHINX.

S. BOTTONE. [73769.]-Pressure on Dock-Gate.-To deter[73761.]-Enamelling Cycles.-"Inquirer" mine pressure on above it is necessary to find the ill find exactly what he wants, with an illustra-average pressure upon a square foot of its side, and on of suitable oven, on p. 172, April 20, 1888. multiply the product by the area of the gate in square feet. For example, a cubic foot of water weighs 624lb., and as the gate is 10ft. high, the pressure on a square foot at the base would be 10 x 62 625lb.; but the average pressure on the side would be half that, equal to lb., which multiplied by the area in square feet of the gate 10 x 10 x 625 equals = 31,250lb. pressure on the 1 x 1 x 2 whole side of the dock-gate. Similarly, to find the pressure when the water is 5ft. high, 62 × 2 = 645 average pressure in pounds on gate, and 625 × 5 × 10 7,812.5lb., which is the number of pounds the gate would be relieved. Subtracting 7812.5 from 31,250, we get 23437 5lb. as the pressure the gate only has to bear now. B. W. L.

[73762.]-Grindstone. -Your stone requires imming dry with a piece of square steel, used ndways to give it a rough face, and trim it perectly straight. SPHINX.

[73765.]-Wire Coils: Why Better than
olid Ones ?-To MR. BOTTONE.-1. Because iron

ire can be annealed much softer than iron rod.
. Because owing to the discontinuity of the iron
ires, the magnetisation and demagnetisation is
uch more sudden and perfect, no cross currents
eing set up in the core itself; hence the alterna-
ons can and do take place much more rapidly, and
he coil is pro tanto more effective. The coils with
Fire cores to which you have compared your solid-
ore coils must have been very, very bad for you
ot to have noticed the great difference in results,
hich amounts to quite 50 per cent. in favour of
he wire core.
S. BOTTONE.

[73765.]-Wire Coil.-In reply, no doubt you ot your coil to work all right, as you suppose, by sing a solid core instead of iron wire, but the eason in using wire is this:-First of all, the urrent from secondary coil depends on its strength, aused by the sudden change or cessation of primary urrent and magnetism, and by using a bundle of con wires for core, each piece of wire loses its aagnetism instantly, while in solid cores the magnetism impedes the primary current, and estroys the full effect of induced current, as I lare say you know the current from secondary wire oil is momentary. You can easily test the effect of ach by using a vacuum tube. The construction of ores as above only relates to induction coils.

MICK.

[73766.-Rubber Spring.-Pure rubber should not be kept in water; but I do not think that the lurability of vulcanised rubber is lessened by such reatment. A common article will rapidly deteriorate under any circumstances.

SM.

[73767]-Safety-Valve.-Nobody can tell you without knowing the diam. of the valve itself.

SM.

4 x 1 x 1

=

[73770.]-Winding for Armatures.- As you
do not say what output in volts or ampères you
wish your machine to give, I can only give you
rough approximation.

Wind the armature with
about 6oz. No. 20, and the field-magnets with 3lb.
No. 22. Connect up in shunt. Let the cores be
2in. wide, 4in. high, gin. thick, with rounded
edges.
S. BOTTONE.

[73771.]-Self-Induction.-This is much too
big a subject to answer in a reply. The whole
matter has been so mystified by the theorising of
mathematicians, that scarcely any one understands
it thoroughly. In truth, there is no such thing at
all: it is a misnomer for the magnetic reaction of
the air, and, therefore it does vary with the current.
When the new unit, the Henry, becomes popu-
larised, the subject will be more studied. So-
called self-induction is first the energy taken up in
magnetisation of air and the wire itself, which re-
appears as electro-motive force generating the

THE WRITER OF THE ASTRONOMICAL NOTES. [73772.] Setting Transit Instrument. Without answering the specific question which "Amateur" addresses to the Writer of Astronomical Notes, I may perhaps be permitted to say [73767.]-Safety-Valve.-I suppose this is one that if he finds any difficulties in setting a small of the ordinary open lever valves, in which the transit instrument, I will be very pleased to help valve and weight are both on one side of the him if he will publish his address. There are a few ulcrum, and with a seat slightly bevelled on its little details to attend to if the best results the instruupper part. Then multiply the area of the valve ments can give are desired, and it is possible that in square inches at half-way up the bevel by the may not see his way quite clearly. pressure of steam in pounds per square inch, and At least, judging from the terms of his question, from this subtract the effective weight of the valve it seems likely that the experience of others would and lever found by attaching them to a spring-be of assistance. balance just above the position of the valve. Mul- 61, Fairhold-road, Stamford Hill, N. tiply this weight by the distance from the fulcrum to valve in inches, and divide by the weight of the safety-valve weight, which will give the number of inches from the fulcrum for that particular weight. Coal is cheaper and better than coke for a boiler. SPHINX.

so short in proportion to its diameter, you will not
[73773.1-Dynamo-Winding.-The drum being
be able to use a larger wire than No. 18 to get 50
volts at 1,250ft. angular velocity per minute. This
will carry 3 ampères safely. It would be hardly
worth while compounding so small a machine; but
suppose you try 3lb. No. 16 for the series, and 101b.
No. 22 for the shunt coils, you will not be far
out. Cores 7in. long will take the wires.

S. BOTTONE.

[73776.]-Parrots.-I have had a large green bird from India in my possession for sixteen years, and he has occasionally suffered from sneezing caused by cold draughts of air. Plenty of red capsicum should be daily given to these parrots. Their eyes should be never near a door, but placed before a window in a sunshiny aspect. Oily food, such as Brazil nuts and filberts (fresh and sound) given frequently. A stout cover of felt floor-cloth should

always envelop the cage until the nights grow warm, and I need hardly add that the room should have a fire therein from October to June-day and Eos. night.

[73777.]-Painting on Zinc.-The reason why paint does not adhere is that the surface of zinc is smooth, and holds firmly a film of air which painting does not remove. This air, and any moisture which finds its way in by capillary action, expands, producing blisters and stripping. The remedy is to produce a coating which is a true part of the zinc surface, and unites with the paint. Oxy-chloride of zinc, chemically formed on the zinc, forms an irremovable coating, and also a paint uniting with but Böttger's is the simplest: 1 part each, by the oil. There are several means of producing this, weight, of chloride of copper, nitrate of copper, chloride of ammonium (salammoniac) and hydrochloric acid, dissolved in 64 parts of water. Brush the zinc over with this, and allow it to dry for at A dark grey least a day-two days are better. coating forms, which is oxy-chloride of zinc, firmly attached, mixed with fine powder of copper, then paint with any good oil paint. The duration will depend on the quality of the paint, as in any other case; but the adhesion will be perfect, whether the paint is of the best or not. I had all my new guttering and spouting treated inside and out 12 years ago. That at the back of the house has never had anything done to it since, and it is perfect, though not nice-looking now, and the inside coating has protected the zinc from any damage by rotting leaves, &c. SIGMA.

needed to keep these in order. The only precau[73778.]-Gravity Cells.-No special care is tion which should be taken is not to shake the cells. Why do you wish to prevent copper being deposited on copper pole of battery? It only increases thickness of plate, which is helpful. It is the zinc you want to protect, and for this reason I recommend lead for the pole, which is a great improvement on gravity cells.

F. ASKEW.

of Fuller's battery. Place the amalgamated zinc
[73779.]-Battery for Lamp.-Use four cells
rod in porous pot, and carbon plate in outer jar.
Charge the latter with chromic acid 3oz., water
1 pint, vitriol 3oz.; the porous pot with acidulated
See also replies to similar queries.
water 1 in 12. This is for a six-volt 24c.p. lamp.
F. ASKEW.

[73780.]-Electro-Motor.-B. and S. signify
Brown and Sharp's, and is an American wire-gauge.
A 12-division commutator will answer just as well.
See above for making chromic-acid battery (73779).
Use two layers of 22 d.c.c. for primary, and 4oz.
36 s.c. for secondary, for țin. spark; for in. spark
use 6oz. 38 s.c. for secondary. Primary same size
F. ASKEW.
as above. Use condensers.

[73782.]-Bulbs.-Whoever told you that bulbs do not produce seed (meaning the flowers, of course) knows nought. They all produce seed under favourable conditions; but that seed needs a long time to germinate. As you say, How can hybrids be obtained except by means of seed? Two or three years would be required after the seedlings to get some to bloom. Certainly, many of the common bulbs are virulently poisonous; but the lily bulbs eaten by the Japanese are harmless, though scarcely NUN. DOR. profitable as food in this country.

[73782.]-Bulbs.-Bulbous plants produce seed the same as any others. You may easily see those

of daffodils after the flower dies. You will find directions how to grow various bulbous plants from seed in any good gardening book; but it takes at least two years to reach the flowering stage of most. Cyclamens sown now may bloom next spring; at all events, I am trying to get some to do so; but success would be more likely in a country greenhouse than in town air. Lilium auratum at 6d. per bulb would be rather dear eating.

SIGMA.

[73782.]-Bulbs.-Nearly every known bulb under favourable conditions produces seeds; but the ripening process is deteriorating to the plant; I clip off all seed-vessels with scissors directly they are formed, thus devoting the juices which would be wasted to the improvement of the future flowers. For instance, the onion and the daffodil seed abundantly

-the new and valuable varieties of the latter are

just now being raised in this manner. Only the professional florist devotes his time to such results, for some seedlings take years to attain maturity, as in the case of Dutch hyacinths, and most of the exotic lilies. A large majority of flower bulbs are highly poisonous, especially the Liliaceae and Amaryllids-beware of them, I say. I am finding rats dead and dying, after their recent ravages in my borders, where they have scratched up and devoured sundry bulbs just springing into leaf. Eos.

dificulty seems to be, many people do not know where to look for them. In this case, the ovary is at the base of the perianth, just beneath the surface of the soil, nearly on the top of the corm. Every perfect flower produces seed; in fact, that is its function-to perpetuate its species. The lily has an ovary either trilocular or hexalocular. Within this we find the ovules, and if these arrive at maturity, we have the seeds. You speak of hybridisation. This may be accomplished as in the rose, by grafting the ovules of one species into those of another whilst growing. It is an operation requiring great care; but, when successful, repays the trouble fourfold, such beautiful shades of colour being obtained-really exquisite. I have had great success with roses, but have not attempted to hybridise lilies. Most lily bulbs are edible; they should be cooked like a potato. I have tasted them, but do not care for the flavour.

=

CH22O17+ 4H2O 3H,C,H2O, CH12O6. Tannic acid. Water. Gallic acid. Glucose. FREDERICK DAVIS.

86, Newington-causeway, S.E. [73788.]-Tree-Stump.-"H. S." will find the best plan to blow out a stump is to use a small dynamite cartridge. Put it on the stump, cover it with a sod, explode with a slow fuse; after lighting which he must run away as fast and as far as he can. If successful, he will, after the explosion, have to look very minutely for any remnant of the stump. No auger-hole is required.

PINTO.

[73788.]-Tree-Stump.-You will waste much time and labour in blasting with loose gunpowder put in auger-holes, the force required being very uncertain. The American apparatus, cheap and simple, does it well, being a hollow steel screw plug 3in. long, tapering to lin. The top end of this plug is made square so as to turn with a wrench into the auger-hole. This is charged with powder before screwing in the plug. When this is done the hole in square end is primed with meal powder, and a slow match affixed. A heavy slab of wood is put over the plug to prevent it being blown away by explosion. I have no time to send illustration, but any smith could make one.

Eos.

You ought to silver

depending upon the specific gravity of the substance and render it very brittle.
used. Barometers made in the manner described plate them if you want to save yourself work.
are not strictly accurate. The length of a glycerine
SPHINX.
barometer would be a great drawback to its general
adoption, the specific gravity of glycerine being with mercury, and if you do not want to get into
[73798.]-Steam-Taps.-No, you can't silver
1-26, whilst mercury is about 13.6. You can ascer- trouble, keep your mercury and gun-metal as far
tain the length of a barometer made with any other
substance than mercury by taking the mercurial apart as possible. If you get trying experiments
barometer as the standard (30in. or 760 millimètres, the opportunity of doing so twice.
of the kind suggested, you will probably not have
and normal temperature 60° F.), and stating as a
proportion sum with the sp.gr., glycerine baro-
meter works out at 26-9ft. FREDERICK DAVIS.
86, Newington-causeway, S.E.

[73794.]-Telephone. Your telephone has evidently been constructed right, but requires proper adjustment. In the telephones I have the boxwood bobbins are in. wide, and depth of channel in. This is filled with No. 36 8.c. wire about 28ft., but as yours is cotton-covered, I don't suppose you could get on more than 24ft. The cotton covered wire will do just as well, but you had better soak it in melted wax after winding. The induction currents from these instruments are so weak that it scarcely needs any insulation beyond the wire covering; but as the best results are obtained by winding the wire as close as possible to the magnet, one is able to do this by using silkcovered. Well, now, we will suppose your telephone completed and only requires adjustment. Take off the mouth-piece and adjust the pole of magnet, whether by screw or otherwise, until the magnet's distance is a little more than a postcard's thickness from a chisel or steel square when placed across the top of case; afterwards fix magnet in position, place on diaphragm, and screw on mouthpiece. You will find that if you could possibly see the face of magnet and diaphragm inside, the proper distance would be just right, consequent telephone does not speak then, I don't know what upon the attractive power of the magnet. If your is to be done. I have adjusted several in this way, and have acted all right first time; in fact, I have a pair of rough-made instruments whose adjustments were fixed by means of glue some seven years ago, and still speak as well as ever. You can generally tell if your adjustment is right by whistling into the mouthpiece a tune: the diaphragm will give an audible vibration to some note to which the diaphragm has been pitched.

MICK.

SM. [73799.]-Copper Plates are steeled by electrolysis. It gives them a hard surface. SM. [73801.]-Dynamo.-Your proportions are fairly correct, and should give good results, if your iron is S. BOTTONE. soft and good. [73803.]-Laminations.-Use iron washers. F. ASKEW. [73803.]-Separating Laminations.-In your case you would find cardboard washers the best. S. BOTTONE.

[73804.]-Tempering Small Springs.-If these are small spiral springs, harden them first by heating and plunging in water, then tie them together with a piece of iron wire, and put them in an iron saucepan or any other suitable vessel, together with oil or tallow, place it over a slow fire, and slowly continue the heat until the oil takes fire and continues to burn. Lift them out and give them a dip into some cold oil; then let them cool in air.

SPHINX.

[73806.]-Model Boiler.-If you keep an equal amount of steam pressure in both boilers, you will have nothing to fear by connecting them to drive your engine. You may make the connection with two bends and a T-piece; or if only small, perhaps one copper Y-piece would be better; and while you are about the job have two starting valves, one to each boiler, so that you could work either or both, and be able to stop one boiler in case they contained A. MORGAN. unequal pressures. [73808.]-Trouve's Lamp.-Try Mr. Bottone's new depolariser; it is capital. F. ASKEW.

UNANSWERED QUERIES.

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

73248.

78266.

[73795.]-Dynamo.-Your wire is too thick for 73269.
this size machine. Re-wind with 24 s.c.; put 12oz. 73283.
73284.
on F.M.'s, and 3oz. on armature. Set your brushes 73292.
at the proper angle, and drive at 3,000 revs. per
minute; you will get about 20 volts and 2 ampères.
F. ASKEW.

[73795.]-Dynamo Machine Defective.-The
reasons for your failure may be many. Among the
most likely are the following:-1. The field-magnet
wires leak on to the cores; test this by sparking
with a battery. 2. The armature wire leaks on to
the armature; test this by sparking with a battery
3. The heads of armature have been made of iron
instead of brass. 4. The position of commutator
slit is wrong with reference to brushes and field-
magnet cheeks. The brushes should be on the slits
when the iron cheeks of armature face the iron
[73790.]-Securing Horse.-In that wide land cheeks of field-magnets. 5. The magnets have not
of equestrian outings-South Africa, "knee halter-been magnetised. 6. The field-magnet wires are
ing" is the popular mode of fastening horses, with not properly connected to brushes and terminals.
a rein or long strip of raw hide, well oiled to make 7. The insulation is bad between the cheeks of com-
it soft. I prefer leather leg collars, with buckles mutator.
and straps, lined with thick felt (like light
"hobbles"), which I used in India. A "knee-
haltered" horse can only walk slowly, yet he will
sometimes creep away, so that a head-stall with a
halter is a good addition by the roadside. The
forelegs and not the hind are to be secured; in the
latter case they are only used by cavalry, with heel
ropes, to keep their chargers in line.

[73796.]-Shocking

S. BOTTONE.
Machine. Supposing

that insulation and all else as stated by you are in
good order, it may be that the spindle is not
insulated from the frame at the end near the spring
which picks up the current. Perhaps the wood
insulation between the two halves of the spindle has
broken down. Have you tested this with battery
and galvanometer? It may be that the spring
presses on the break piece at the wrong time. The
interruption should take place when the bobbins lie
right across the two poles, and not when they are in
a line with the limbs.
SM.

Eos.

[73792.]-Alcohol in Wine.-Certainly it is possible. You must add carbonate of potash until the wine is saturated. The alcohol will, on standing, float to the top.

[73792.] Separating Alcohol from Wine.Add as much carbonate of potash (salts of tartar) as the wine will dissolve with shaking. The alcohol will be contained in the floating liquid. P. H. POLGLASE. [73793.]-Barometer.-It is essential that the glycerol be quite anhydrous; metallic impurities are of no consequence. You can use oil if you like, but your barometer tube will have to be 40ft. long. SM.

[73793.]-Barometer.-" Doctor" will find the commercial glycerine answer every purpose as a barometer. Any oil or fluid that is stable will also answer the purpose, the length of the barometer

S. BOTTONE.

Mandolin, p. 363.

Skeleton Skates, 363.
The Physical Basis of Music, 363.
Examination, 363.
Stereoscopic Camera, 363.
Ballistic Galvanometer, 363.

WHATEVER steam the injector uses in doing the mechanical work of forcing in the feed water is no doubt well enough used, but the whole amount of steam drawn from the boiler is out of all proportion to the work done, say four times as much as a nonmost of the steam is used simply to warm feed expansive, direct-acting steam pump requires, and water.-J. BURKITT WEBB, in Power.

The Respiratory Centre.-The details of a research of considerable importance, undertaken by Laborde with a view to determining the situation of the centre for respiration in the medulla, are given in a recent number of the Comptes Rendus. Full particulars are promised in a more elaborate form. It was found that superficial destruction of the al cinerea produced impairment of respiratory movements; deeper injury produced slowing or temporary cessation of breathing, while destruction, at least down to the centre, This condition was produced with the greatest gave rise to complete suspension of respiration. certainty when a particular part of the floor of the has a diameter of 0.5mm., in dogs of 1-2mm.; bat fourth ventricle was removed. This part in rabbits the instrument must penetrate at least half the thickness of the substance of the medulla, and pass to the raphe immediately above the calamus scriptorius. Destruction of this region on one side suspends temporarily respiratory movements of the opposite side of the body. Division of the medulla just below the calamus always suspends the respiratory movements of the trunk, those of the head persisting for a time. The movement never returned if nothing was done, but it did so if artificial respiration were kept up for a long time. The spinal reflexes remained present, were even increased, and there were superficial, irregular, but ineffective contractions of the respiratory muscles. In newly-born animals the exaggeration of the reflexes was especially marked. All parts above the medulla, including the cortex, the corpora quadrigemina, and the optic thalami, were found to have no particular influence on respiration.-Lancet.

[73817.]-Electric Coils.-I am in difficulties. Will Mr. Bottone, Mr. Allsop, or any other of our electrical readers help me? 1. I have a machine consisting of two vertical coils about Sin. high, a spring contact breaker, and also a mercurial contact breaker. What is the nature of the instrument? Is it an induction coil or shocking coil, or what? Why should there be two coils and two contact breakers? How is the power of current regulated? There is no lever or slide. It has also five terminals, two on one ide and three on the other. Which are the proper ones to connect to battery? What battery power would be required to work it! 2. Is there any means of converting vertical shocking coil into an induction coil? Is it possible to use a shocking coil as an induction coil for experimental purposes-that is, is it possible to get sparks From a shocking coil? 3. I should like to have instruc--G. J. J. tions for making the rotating part of a mercurial contact

now something else. If one volt can force one ampere following in a plain way, explaining the method? An spondent give me the rate of expansion of ebonite for

breaker, thickness of iron core, number of layers of wire,
&c. What part of my machine No. 1 is gone? Any
help will oblige, as I am practically only a novice.-CON-
[73818.]-Electrical Units.-To MR. BOTTONE. JAY.
Thanks for your reply, which is very clear. I want to
through one ohm, how many ampères can two volts force
through one ohm? Taking an ohm to be a yard of No.
40 wire, it will safely carry one ampère driven by one
volt, but if we were to try to put through 100 volts and
100 ampères, that wire would cease to exist. Also what
should be the resistance of a 100-volt lamp?-Q.
[73819.] Dynamo Calculations. To MR.
BOTTONE.-In calculating the resistance of the wire on the
armature, in your book on "Electrical Instruments,"
page 114, you say of 56yds. Why is this? Second, with
respect to instructions on field-magnets, page 115, you
multiply the resistance of armature 25 by 400. Where
does this big number come from, and how is it arrived at
No explanation is given-one is much needed. Is the
outer circuit resistance, named on page 114, 11 ohms or
not! If you will kindly give another example of this
class, and give values all the way through, instead of
leaving a novice to guess at them, it will doubtless be
appreciated.-No CAN SEE.

[73823.)-Petroleum Engine.-Would some corre-ing? What is lithanode, and how is it made?-S.
spondent please give a description of the apparatus for
generating the gas for these engines, and of the valves
and igniting arrangement! I wish to make one-about
2-man-power, for driving lathe, &c. Would be glad to
know size of cylinder for this power. I understand con-