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Science" implies (p. 648), I call it a most
"clumsv" expedient, not meaning by that
term jiuiefurot* bnt inorlijfcial, or in the sense
that wo call it clumsy of Chinese water-
carriers to inherit the contrivance of a yoke to
which they append a bucket of water at ono end
and a atone at the other, and are said to have
organized as stout a resistance as if they were
Manchester or Sheffield unionists, against the
innovation of balancing one basket by another.
Let A be the present level of mercury in a
simple rigid cistern, anil B in the tube, SOin.
higher. Suppose tho surface A to be nine times
the area of B. Then if the top were opened,
both surfaces wonld come to the level C, three
inches abovo A. Now, if the makers expect
rue to bring "tho fluid in tho cistern always
to tho sumo level when an observation is
made," I beg to tell them and "Exhibitioner,"
I prefer tho less troublesomo course of ob-
literating their scale, and making a directly
usable one, by dividing the 27in. from C to B |l
into 80 nominal or senie inches; in short, figur-
ing every 9-10 of an inch above or below B
as an inch. If they object that the tube or
cistern arc not parallel - sided, I say they
ought to have been so practically and that
their not being so is most " clumsy."—E. L. G. —

[•1484.] — BUNSEN'S BATTERY—"An Old Subscriber" will find tho easiest mode for cutting his caibons is to fix his carbon in a vice and cut it down with a hand-saw. The saw will cut about twelve, then will require re-sharpening.—A. J. Jarman.

balls, or other light substances, the other, after^leaninh the grain from remaining impurit.esalter_being »£°uTM (each acting independently of the other), depositing two kind" of screenings, one taken from the wheat before it U stured, the other after, and both etomv-dhom •last and chaff, and ready for market. Tie WW" constructed on the smooth surface principle »?\therefure is not liable to break the wheat, which is a great drawback to rough surface machines. It ordered they attach a shaking shoe, as seen in cut No. 1, the Urst screen of which is for the Panose of carrying off any impurities larger than the grains of wWUTta second screen separates tho sand, seeds, 4c. With this sue* the machino forms a complete grain cleaner of i*»UWith regard to fixed i>. balance rhynds I should think the increasing scarcity of the fixed 'bynds will be answer enough, being almost entirely superseded by tho balance.—Ssrgicb.|

rt4091 — FOUL AIR— It is a most mischievous error to suppose that wherever a light will burn a man can live A candlo would burn to its ond in plenty_ of glseous mixtures that would °e ««««»< death to any wirm-blooded animal entering them. No man should b ■ allowed to descend into a well, a liquor-vat, or any D ace Tit for many hours without downward outlet, till a bird in a cage has been lowered for some minutes and drawn up alWe. Tho only reason why ascending into an untried upward well, or place without upward outlet, "less dangerous than descending an untried downward receptacle, is because light gases have a far more active diffusive power than heavy ones. It is providential that carbonic acid, tho commonest by far of all lrrespirable ones, is heavier than air of tho same temperat are, but comes from all its ordinary sources,, as animals lungs and combustion, heated enough to rise at first. The'above accidonts arise from the comparatively rare case i where it is produced cold. The ordinary warm caroonic acid, nearly as fast as it can "ccumulate against r.ofs or ceilings, must cool and descend, so as to be quickly spread and diluted. StiU, no lantern, from a 1 ghthouse to a policeman's bull's-eye, is made without perfect upward drainage, for its continual outflow. IndeedI every lantern maker knows that not one would be saleable without it. No par-icle, of air can enter any lantern twice. In all our dwellings, on the contrary, ,md most public buildings, the ceilings are the most perfect arrangements that could possibly be contrived or retaining and forcing all foul air to be breathed ..vor and over again as many times as possible.E. L. G.

IM15.1-CURIOUS PROBLEM.-According to the augers received from various sources it^would.. wear that an "irresistible" force cannot co-ex.t with an '• immovable " body and »i« ««; m other wolds, I1m terms are incorrect, and as definitions of «"»«s *h'cnu have no existence should be crossed out of the dictumary, or at aU events become obsolete. To avoid such_« conclusion mv <.'t,r eno suggests that an .'"e^bU force cominR into contact with an "'■"u»0TMbJ« object would "make a bole through it! —Sael K\mka.

[4474.] -HORSE POWER.—" Vertumnus" <P- »J8), gives tomy mind rather ..curious rate for Ondia^Uxe V.orae power of a cylinder. May I ask hun if the a trokeis not worthy of some little consideration. To >Um*rato this I will take his example, viz., a 6in. cT^ef- lt ""J have Sin. strike as iu a locomotive oMlin.jas in a screw engine, and by his rule the two cylinders are of exactly the same power, whereas in reality the 9m. is exactly double the power of the other.—1>. w. A.

[4481]-THE BAROMETER "DIFFICULTY."-!.was •war? that standard barometers have »«y*»»? ending downwards iu the point mentioned by A. M. w. p. 071), and by thus separately measuring tie different ,ff level at everv reading, we eliminate tho effects ot any ue'm'lity of boro in different parts of the tube or "s?ern ^But if this is expected to be done withicvcry barometer, as "Exhibitioner at Royal College of

[4495.]—GOLD SHELLS.—These may be made by rubbing up Bold leaf with thin gum water and spreadLug upon shells. The gum used for this and colour grinding should be tho finest white gum arabic dissolved iu distilled water. The palate knife should touch this and all the mineral colours, especially the vormillion, as little as possible. Beware of dust in all such operations. —Sablk.

[4501.]—SEWING MACHINES.—As "J. G.'s" reply f i f he gave one) to "H. W." has escaped my notice I will see if I can be of assistance. As well as I can judge, tho fault is still a badly-regulated tension of the upper thread. "H. W." should gradually increase the tension till the loops vanish, or good thread breaks. His remarks read as though his machino had no tension attachment, else the hole in the cotton-reel would have no need to be made smaller. If this is the case, " H. \\. might manage to increase the tension by giving the thread ono or more turns round the thread guide. "H W " had better not take bis machine to pieces till he knows it better, or he may spoU it altogether. If regulating tho tension does not make it all right, let him see if the brush has been pressed iu on the hook too tight—this would aptit the brush and make it useless. Or the pin at tho end of the rod which drives the rocker may have worn loose, and if so, it may bo made right bv (riving the screw an extra turn. P.S.—1 hope "Practical Man " will soon let ns hear from hun with the promised information about sewing-machine construction.—AQUILLU8.

T45041 —ELLIPSES.—The common trammel (or elliptical compass) has been described and figured several times in the English Mechanic, better than by T.W Boord in this number (p. 548). Thus in vol. VII. alone, I And it rightly figured by " Novice Barnsley, p. 193, as well as tiestill simpler mode of striking ellipses by foci and cord, three <i»«» given, >>p. 148, 149, J14 , and a third method on a wholly difforent principle, p. 45J. Moreover the "connecting-rod "oval that our Present "J K P " patronizes, is there also confounded with an ellipse, or an" ellipse in perspective," pp. 237, 328, and its first introducer, Thomas Arnall, even callshis in; strument for striking it an •' cUiptograph. J. K. r. must surely see that if it be ever egg-shaped U must alwag. be insyninietrial and a more complex curve than tho ellipse however, long his connecting rod. In fact, it fan oZof the fourth order, while ellipses and all come sections are of the second, tho same order as a circle. T WBoorf"figure of the trammel has been made puzzling by tho printer inverting it, bnt is also wrong bv having the arms of tho cross unequal; and an attempt to disguise the inherent defect of that instrument w-hich is, that owing to equal length of grooves being required each way, you cannot strike any ellipse with a minor axis less than the width of the cross, nor can you strike one much wider than the instrument, nor so Lug as twice its width. In fact, only ellipses of small eccentricity can bo drawn by it, and the larger the less elliptic by suppressing ono arm, however, or rather uSthleuS cross,;we canjta^-U^

was doubtless occasioned by a current of hot air rising from the roof.—Unit.

[4519.]—PHOTOGRAPHY.—Ordinary shellac dissolved in spirits of wine makes a good and cheap negative varnish, to be poured on to the warmed plate the same as collodion. Or the hard spirit varnish, made for carriage painters, diluted with twice its quantity of spirits of wine, is good.—Unit.

[4521.]—EXTRACTING HONEY FROM THE COMB. —The method I adopt is to stretch a coarse strainer over the top of an earthen pan, open the cells of the comb with a knife, and cut the comb into pieces. Then place it on tho strainer, when it will drain into tie pan beneath perfectly clear. This is the most simple and the most perfect plan I know of.—Winnbb.

[4580.]—HORTICULTURAL—"G. H." in pruning gooseberry and currant bushes must be guided by the Btrength of the soil. At any rate, all main branches that crowd one another should be thinned out, and only as many left as tho root can supply. After reducing the main stems, take each one separately and cut the side shoots down to spurs about an inch long, of course removing all weak and spindling shoots.—SArL Rymea.

[4539.]—CHIMNEYS—In reply to the inquiry of Mr. Moody in your journal of the 19th hist, (query 4539), I beg to give him below tho principal dimensions of a very elegant and efficient chimney-shaft erected for four (eventually for six) boilersof about the same size each as those described by him. The chimney is built of brick; foundation and plinth four =, and equal-sided; shaft octagon, in horizontal section. Tho foundation is 261ft. deep, forming an equalfour equal-sided prism of 14It. 8in. side. Tho plinth is 19ft. 8in. high by llMt. side. The shaft is 92ft. high from top of plinth, Bo that t.

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shaft is aait. mgn irom mp ui imuw, »"'""- .r,:~ , height from ground-level is 111ft. 8m. The width of flue at base is 69in., and at top 89Jin. The thickness of masonry in plinth is S94in. and in the shaft at lower end 29.1in/and at top 10. Plinth and shaft is cagpe-d with hewn freestone. The canal from boilers leading into base of chimney is immediately under ground-level, and is Sft. 6in. high by 4ft. lin. wide.—E. W. A., Cologne.

[4541.1—EMBROIDERING MACHINE.—There is a machine special for this, but very dear. There are attachments for the same purpose to some makes oi "Wheeler & Wilson," also to " Slncor's," and perhaps tho "Weed," and the "Howe." Bradbury s W. W. makes, so I understand, six different stitches; ranging from single thread chain stitch to eitiht thread embroidery Seller's W. W. uses up to«r<r thread embroidery stitch. I consider the "Gulph treadle tho best chain stitch machine. Perhaps it would suit A Braider," but chain stitch is rnii embroidery stitch.— Aquillus.

r4545.1— SECRET CODES—In compliance with the request of "Argus," I send you the olue to the "secret codo" upon which I commented in your columns lu No. 278. To take the simplest case, let us suppose that the suspected wordia the first in the cipher, and is believed to be BEACH ; the corresponding letters in the cryptograph being ULOTU.-We proceed as 'o1Jow8.:-1j>V Write down the alphabet in order as far as^the lowest letter in the word-i.«., as far as H-«nd draw under it as many parallel lines as in the suspected word 2nd. On the first lino place U under B, on the second L under E, on the third 0 under A, on the fourth T under C, and on U?e last II under H-i.*., the cypher letters, one in each

■e under the suspected letters. 3rd. Complete theso lines iu retrogradealphabetical order towards the left as f ar as the column under A, and the first column give, tho kev Thus ABCDEFGH&c.

HIJKL &r.
O&c.
R 8 T 4c.

NOPQRSTU&c. Showing tho key-word to be THORN. Iu the second case suppose that the word is not the first, orthsttbo sentence begins "The beach." Our first, seoond, and third trial will fail, but the fourth wiU produce this resultcipher being SRTJV—

ABCDEFOH...
RS . . .
SOPQB...

T

HU . . ■ •
OFQRST UV . . .

which gives RNTHO as key-word, which by an easy trans ,os tirfn becomes THORN. If the known word be lolScMh»n"he keyword, the latter will repeat Itself, thus THORNTHO; if shorter, we must guess at the

word may falf into the hands of others. Allow mo to ad I that* I have invented a litUe *"«tn» "^

terest Hm send a sketch, with full permission for any oTto' mike Tor private use. or for saba as I .».merely

one founded on the principle that I .haJ0 *"?rt,t0 * ,lin. date, the other upon the same principle, with » modin cation which I have introduced. I may »? t^'w»a * >t word in each i# a very common word, and J TM*[JnJ that the word JONES occurs in both. If »?yD1oju"r crv .togJapher on discovering my plan wdl tajy«; affik method taw A ob hge »«TM»,*'»JgnJJ

objection— „ _ a T*«

■, * r> *^«-«m 2nd Improved Do.

YMNfA^sf^SYG Kuopfcqssmtlgpfyul To conclude for the preheat, as an old rhyme gays, a perfect cryptogram should be

"Easily written, easily read,
Easily carried about in the head."

Although the easy reading must not apply to the side of uhe enemy as well as our own.—Cryptographer.

[4556.]— TELEGRAPHY.—Nearly all telegraph-posts have now lightning-conductors, they have also "guards" to retain the wire from falling and coming into contact with other wires in case of an insulator being broken. It is probably the former "Mos" is inquiring about.— Unit.

[4559.]—HORSE-POWER OF BOILERS.—Find the area of water surface freely exposed for tbe evolution of steam by multiplying the length of the boiler by the length of surface lino, measured across the glass gauge, which in this case should be at least 6ft.; divide this product by 478 square feet for the horse power. 324 x 6 Consequently —4.78— "■ 40'78 H.P.

Note.—The absolute value in horse-power of 1 cube foot per second, indicated boiler pressure 40lb. per square

461b. inch, is o.LMirr = 10*46 H.P. per cube foot. And the area

of water surface divided by 7 is equal the number of cube foot can be evaporated per hour from such boilers;

321 x 6
.*. —7~ = 28 cube feet,

allowing 1 cube foot of water to each square foot of
furnace, 28 will also represeut the area of furnace in
square feet. Therefore, the relative volume of 401b.
steam being M 500, we have 28 x 500 =.14000 cube
feet of steam per hour.
14000
Consequently «o "^ flo — 3"9 cube feet per second.

and 3-9 x 10"46 = 40 78 H.P. also.—R. D.

[Seo also letter headed "Boiler Power" in this number.]

[4561.]—ENGRAVING BRASS PLATES.—Mako the plates hot enough to melt red, black, or any other coloured sealing-wax that may be desired, and run it in. Chip it off the surface, where not required, when cold.— Unit.

[4568.]—WEIGHT OF RAILS. — "Ferrum" should multiply the cross section of his rails or Tee-iron by 3'3 for iron, and by 3*4 if for steel, which will give him the weight of a lineal foot in pounds, and multiplying that by the length of the rail in feet will givo him its weight. —G. B. D.

[4569.]—ESCAPE OF GAS.—It is a fact that when any holder is left undisturbed (viz., the inlet and outlet closed with water) for some time, that the gas will diminish in bulk. "W. C.'s" holder having stood so for nearly six monthB, I am not surprised at his loss. I send three practical reasons, which, taken together, will quite account for it. 1st. Is the holder thoroughly coated with pood point? If not, a large item is accounted for, as it is well known that gas will escape from one not painted, allowing that the joints are perfectly sound. 2nd. The holder has been exposed to the full heat of summer. The heat of the sun causes the gas to expand, thereby " drawing the holder up," causing it to " blow." 3rd. I will venture to say that there is a quantity of oily matter floating on the surface of the water inside, if it has not yet shown itself outside. Gas consists of hydrogen and carbon, holding in suspension a number of condensable hydro-carbons, which by the varied changes of temperature, would be condensed, and form the oily substance above-named, thereby causing a diminution of volume. Were I acquainted with the size and situation of " W. C.'s" holder, and furnished with an answer regarding the first reason, I might write with more certainty; as it is, I only send the above facts for his consideration.—H. N. H.

[4572.] —GEOLOGICAL.—" Philosopher " does not give sufficient data to enable one to answer his query with certainty. Malvern lies on the edgo of a long narrow strip of Silurian rocks; so his limestone is probably of that age. If he can obtain any fossils from the quarry, they would tell him what formation they belong to. The Ordnance geological map of that locality is published in quarter sheets, and would not cost much, and will give the fullest information.—E. D.

[4573.]—METHYLATED SPIRIT.—There is never any difference made in the quantity of wood spirit added to the spirit of wine. As to its quality, by which 1 presume " M. M." refers to its odour, that may at times vary, being dependent upon its rectification and tho heat at which it was originally distilled. The wood spirit must be obtained from the revenue stores.—A Revenue Officer.

[4576.]—BLACK BRASSWORK OF MICROSCOPE."J. Haines" may black the brass work of his telescope with'a mixture of lacquer and lamp-black. This is what I used when putting in two new tubes into a 3ft. achromatic that had been broken by a fall.—G. W. A.

[4576.]— BLACK BRA88WORK.—The inside tubes of microscopes are blackened with a mixture of lampblack and turpentine, applied with a soft brush.— Medicub.

[4576.]—BLACK BRASSWORK OF MICROSCOPE. —Vegetable black mixed with lacquer and thinned with spirits of wine is used for the insides of microscopes and telescopes by all opticians.—R. N.

[4580.]—MANGANESE BATTERY.— Having never compared tbe power of the two batteries, I cannot satisfactorily answer "Northumberland Subscriber."— A. J. Jaeman.

[4582.]—GOLD LEAF.—"Chemicus" should buy a book of gold leaf, when ho will find that the paper is exceedingly smooth, and that it is rubbed with powder of red lead in order to prevent adhesion.—H. W. Revelet.

[4682.]—GOLD LEAF.—To prepare a book of leaf for use out of doors, take a large pair of seizure and cut the back of the book right off as near the Bewing as convenient. Then take up the top leaf of paper and rub the side that was next the gold on the face or hair; lay it down again on its leaf »f gold; pass the hand over it

smoothly and with moderate pressure, aud the gold will be found to adhcro sufficiently; then lay it aside, gold side up; do the same with tne next leaf, and so on through the book. In applying the leaf so prepared, cut paper and leaf together with the scissors, and apply to the work, holding the piece with the poiuts of the scissors at any corner. In this process no gilder's cushion, tip, or knife is required, only a little cotton wool to press down the gold on the work.—Working Woman.

[4588.]— TELESCOPE.—Varnishing the inside of tbe tube with a dead black will no doubt improve the definition of the telescope.—Unit.

[4589.]—TENDER FEET.—The "Pedestrian " should rub the inside of his socks with yellow soap, and wash his feet every other day in warm solution of common salt, aud ho would not complain of tender feet.—Med*

CCS.

[458X]— TENDER FEET.—On long pedestrian tours I have found perfect immunity from blisters or tenderness of any kind by wearing heavy well-fitting boots—not too loose—and thick woollen socks, the latter well rubbed with a lump of soap in parts where blisters are apprehended. Shod in this way I find my feet keep cool and fresh, and holdout while endurance lasts.—Paddy.

[4590.]—TOWN GARDENING.—I should recommend "Factory Lad " and all who wish to grow plants indoors, under the circumstances he describes, to try some of tbe Sedum and Echtctria, or perhaps he will understand better if I say Stonecrop and Houseleek tribes. They are very interesting little plants, and there are many beautiful varitics bearing red, white, and yellow flowers. Their habit is very dwarf and compact, seldom more than 6iu. from tho ground, though the flowers of some shoot up about a foot. I should say they are by far the most suitable kind of plants for indoor culture, as from their succulent nature they are fitted to bear a long continuance of dry atmosphere. As for - .i they will grow in brick and mortar rubbish, or almost anything, and want very little water. For boxes outside windows, I should recommend a few hardy dwarf perennials, such as white pink, arabis, thrift, stachys, moneywort, yellow stonecrop, white stonecrop, corydalis, red double daisy, all of which are compact little plants, and except for the flowers remain the same summer and winter, and would grow in any ordinary soil. If "Factory Lad" would like to try the plants named above, and will publish his address for post and parcels, I shall be happy to give him what he requires. I have some nice roots of them all, fit to move if he is not too far off to think it worth while having them from one of the home counties, in which case he must let me know tbe sizes of his indoor and outdoor boxes, and I would choose the plants accordingly, and would pay carriage as far as I could. I should not recommend him to grow plants from seed; I am afraid they would never thrive without plenty of sun and air.—Working Woman.

nearly colourless scales, when quite port, bw jn^ in water and alcohol with a most intense hpk re» colour. It possesses ajvery bitter taste, and is a i^ present in beer it may be detected by craprjoin.^* of the liquor considerably, adding a few iro^^, sulphuric acid and filtering. In tbe filtrate a^ ^ fibres of clean silk or wool for some time \t±.'-J present a canary-yellow hue, tbe preseaa ■* a _ may be considered as demonstrated. h& , &_ brownUh colouration should be di«*regari^ ;.n,"^ that picric acid is prepared on a large n^lrf2u wool dyeing, and coxts about 3**. per £ f^ some authorities stated to act aa a nco^n^' Trinitrophenic.

r4605.] — PROPELLING A VESSEL Bl u^. MILL,—Mr. Burton does not serin to bn^^, visionary project of propelling A vessel Ol. .' means of a windmill on board is a ecb* J. ancient date. If Mr. Barton objects to i be may adopt a kite provided with the , pliance for striking, in order to bring it don. a> guide-lines, in order to Hail as ships do w,t'.. of the wind's eye. A kite of equXl po*n quire one-fourth of the canvas used in c*Ea*a. —H. W. Rkveley.

r460ft.]— PROPELLING A VESSEL BY l 10 MILL.—I beg to infonn Thomas C. Burt/m uxa years ago I made a model of a windmill for tec both screw and paddle wheels, and tried it npasi«£ boat, and found it to answer admirabrr. It was straight ahead against wind or tide* but 1 then scr*. I could make many improvements iu it, and I an.. a working model, made upon my improved plan, »_ I could guarantee would go double the speed of aa; a. ing vessel. It is very easily managed. One man *k sit and steer, and have entire control over it: can r. here, go ahead or astern, without the least difficult When not required for use it may be left, as it would i< perfectly safe, aud a gale of wind would not have the loast effect on it.—John Jaxxs.

[4607.]—ORGAN BUILDrNG.—Stop dixpaun pipe; are made louder by giving them more wind through the foot hole. If that does not produce tone enough, tai -:off the cap, and with a file opeu the wind-way a littJr. Possibly the mouth of tbe pipe may also require Cumdz up a trifle. Hard brass-wire U usuaflr ased for ffr**1i* —R. W. D.

14609.]—AIR-CANE.—The drswin* Pd p. *30does mi show the stop preventing the latahier fruni turning further than necessary to fit* the tear; the trigger spring is planted the wrong wij,ia4lke ni&iiicpring is not drawn sufficiently high to alto* tor tin twam <A the tumbler. An air-cane is straight, ratawina t\taai 8ft. 'Jin. in length, and unscrewing in the mi&A\t, * shown in the accompanying sketches, which are the proper sizes for a very large one. A A, lock plate; B.

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[4593.]—PIANO PINS.—"Necessity's "strings may bo of bad quality; only first-rate will stand concert pitch. Or they are too thick for their length.—Revkley.

[4599.]—EFFECTS OF CARBONIC ACID.—See G.

E. Davis's letter.

[4602.—MELTING GLUE.—" S. N. R." must steep his glue eight hours in clean water, then put it iu the pot, boil it, and then it is ready for use.—A. SroitMEKr.

[4602.]— MELTING GLUE.—If "S, N. R." will break up his glue iu small pieces, put it iu his glue-pot with a little more water than will cover the glue, then put it over the fire, let it boil until the glue is melted, he will know If thin enough by the brush working light and free on the wood. Add a bttlc water each time he melts it.— J. G.

[4603.]—MELTING GLUE.—Tho proper way to melt glue is to put cold water sufficient to cover it and when softened boil in thegluc-pot; of course if it is kept melted long it will want more water added to it, on account of

ojAporatiou.—R. N.

'[4602.]— MELTING GLUE.—Common glue may bo preserved after melting by adding a few drops of turpentine or of acetic acid.—H. W. Revkley.

[4603.]—FISHING.—Perhaps some among the lovers of the " gentle sport" who read your excellent paper, may like to hear of a plan practised with success by the Thames fishermen when fishing for gudgeon. The following is a description of their tacklo :—A piece of thick wire about lslu. long is to he procured, and loops about the circumference of a pencil to be made at each end and in tbe middle ; a No. 11 or 12 hook must now be fixed to each loop, aud shot must be put about Sin. from each hook. To the loops at tho end two pieces of line about 2ft. long each are fastened, and the other eud joined to the line fastened to the rod. The latter must be a trolling rod, and the angler wades into the river just below the lock gates, and lets the tackle, baited with blood worms, float down stream. Two or three gudgeon arc frequently caught at once. No ground-bait is required. —C. B.

[4601.1—PICRIC ACID.—TO" S.H.B."—Picric acid is made by dissolving indigo in smaU pieces in ten or twelve times its weight of nitric acid, sp. gr. 1*48. When all the indigo has been added, the action is at first extremely violent, after it has moderated, an additional quantity of boiling nitric acid may be poured on, and kept boiling till the red fumes cease. This is theu crystallized. Crystals in yellow needles. Solution of picric acid is used as a test for potash, and used by dyers to give a beautiful green colour to cloth.—Omeoa.

[4604.]—PICRIC ACID.—Picric acid is a nitro-substitution product from carbolic or phenic acid. It forms

barrel; C, bullet; D air way; E E, socket of strikis; pin, shown separately at F; G G, end view of loet showing entrance of airway and end of striking pin i H, section of breech piece, containing the only vah* belonging to an air-cane; 11, brass collar tinned fifr' the copper tube forming the air reservoir. The bre*« is screwed tight into this collar, having a leather watfc; between to ensure an air-tight joint. It is best to commence with the copper tube for reservoir, and thin *btt* Iron case covering the lock and barrel, a< then all toother parts can be better fitted. Be sure the butt endU strongly brazed up, as it has to stand the additiotai force caused by the driving in of the valve.—T. A. v.

[4611.] —POLISHING VULCANITE.— There are" various methods employed to polish ebonite or valcanite ; the mathematical instrument makers treat U as brass—that is, for fiat work they first use water d ayr stone, and then rotten stone and oil. Turned wori is polished in the lathe with rotten-stone and oil, :..-■■■ care always not to use too high a speed, so as ■,...:.■' tbe work. Some use lampblack and oil to finish witfc where a very high polish is wanted, and others, ag*>s the bare palm of the hand, as in getting up silver pi**'Chain and ornament makors use circular buffs for the-1' flat work, made of soa-horse leather, and for work of irrr gular forms buffs of calico. A number of pieces, 13in. u diameter, are screwed together between flanges, like » circular-saw spindle, and used with rotten-stone, taking care always not to heatth e work; brushes are not at &B suitable for it.—R. N.

[4612.]—PORTABLE MILL.—In reply to "D«: Errac," I have a model of a portable windmill or engine for pumping with any description of pumps, or the same might bo used for any other purpose, such as sawio?ploughing, grinding of corn, cutting chaff, or for any purpose where motive power is necessary.—Joss Jameh.

[4612.]—PORTABLE MILL.—I beg to inform "Derf Errac" that I never heard of or saw a portable windmill, except in a toy-shop. Mr. Vallance's plan is that of sailing ships, and must have required almost a hurricane to drive seven ploughs. Windmills for draining wore formerly much in use, but they have long since beon superceded by steam power, as more economical and efficient. Gwynne's centrifugal pumps are much used now, but they frequently blow, and require filling up with water for a fresh start.—Henry W. Revkley.

[4615.] —SEWING-MACHINE ATTACHMENTS. "J. F. R.V machine being a shuttle machine does not show the sort of hem-foldor he wants, except that it will most likely be itft-handt.il. Something depends ou the material he wants it for, and the size of the hem. I hope the replies to "J. F. R." will throw light on this subject for my sake as well as his.—Aqcillvs.

[graphic]

[4616.] PROBLEM.—I am sorry that time will not

allow me to work oat the problem proposed by M Amicus "folly; but I will make all clear for him to do so. He must not be afraid of large complicated numbers and expressions. The question is a solved more easily by trigono

metry, yet as it is taken from "Ne wth's First Book," I imagine the algebraical solution to bo what "Amicus" required. Thus: , —Let the diagonal C B of the D the parallelogram A B C D represent in magnitude and direction the resultant of two forces A C, C D, acting upon n point C nt an angle of 185°. Let A C = C D. Let C B = 1001b. It is required to resolve C B into its components. From B draw B E at right anglos to C D meeting the latter in E. Because AC B = 135 , A K D = I8y, and Cabtcdb=90:> But as they are equal C D B = 45° In tho trianglo BED, the angle B E D = fW°; E D B = 45°, and therefore, D B E = 45"\ i.e., Euc. i. vi., BE = E D.

Let x = length B E, then x = length E D. and Euc. 1, 47, */2x* = length of B D = x ^2, or, "WormelTa Mechanics," the hypothenuso = either side x ^:.BD = m *J~2; but B D = CD (const.), .". C D = x */2~ and C E = x s/%~- T. By Euc. 1, 47, B C* = C E2 + B E3, i.e., 180* = (x*/*-- .r)a + T*. *' Amicus " can solve this equationjind getting tho value of x or BE, he can multiply by *j* to get B D, or

jr2 + x* = B D. p.S.—I do not think our friend will ever get such a difficult problem iu tho " London University Matriculation Papers."—C. H."W. B.

£4618.]—MANAGEMENT OF BEES.—I agree with Tnos. Poulton, that letters on bee culture would be very interesting, and I trust not inappropriate to your columns. If he would fill a wide-mouthed bottle with water or bee food, tie some fine muslin over the mouth, and quickly invert it, he will find none will escape after the bottle is Inverted, and will at once see tho principle of the feeding bottle. The bees suck the food through the muslin from the bottle, as it is inverted over the hole on the top of the hive. Sometimes the bottle is inverted on perforated zinc, allowing it to be removed and replaced, without the bees escaping through the hole at the top.—Astros.

[46ia] BEE MANAGEMENT.—In answer to Thos. Poulton, thero are several ways of feeding bees, but I believe the best feeder is the simplest, viz., a round zinc pan, as per sketch.

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A, zinc pan; B, honey, or sugar and water; C, floating board, perforated with numerous holes; D, entrance for bees ; E, top of hive; F, super or working hive. There is a pioco of wood, which fits into it and floats on the Bugar and water, perforated with numerous small holes through which the bees insert their proboscis, and get nutriment without getting their feet, legs, or wings sticky. The feeder is placed on the top of the hive,and the Lees ascend through the centre. Of course this is used with the humane or depriving system, other than which no amateur or any other bee-keeper should use. With this hive, which is as inexpensive as any.and which anv youth with a little ingenuity can construct for himself, the little bees will produce more honey, and afford a constant and highly interesting study, for any time the bees could bo seen at work through the glass doors. As far as expense goes bees can be kept in an old wooden barrel, providing it is clean, and put in proper position, &c. The simple square box hive, with two or three working supers, ia a very good one, and gives very little trouble to the bee-master, and a strong healthy swarm will work three supers during the honey season. Should my brother readers require any further information on bees and beekeeping I shall be glad to aid them in every way I can if they will ask through your columns.— Frank.

[4618.]— MANAGEMENT OF BEES.—Feeding-bottles ftrr bees are on the principle of the fountain for birdcages. They are readily made. Get a wide-mouthed glass bottle—a pickle-bottle, I usually have—nearly fill with syrup, have a piece of canvas and tie on the mouth as if you wore tying down preserves, only don't have the cloth two thicknesses. The hive is supposed to have a large hole in the top, on this place a bit of perforated zinc, holes about the size of the head of a pin. Carefully turn tho bottle of syrup upside down on this zinc. No more Byrup will leave the bottle than what the bees will readily take up. Sec J. W. Pagden's pamphlet on bees, To make syrup I bny West India sugar, 4d. per lb., to every pound I add half a pint of water, boil for a few minutes, say, five minutes, when cooling stir in a pinch of salt and a few drops of rum. On the 11th July, I had a swarm too late in my district to do any good. I hived it into a box 12in. square, 9in. deep, commenced feeding, each night giving a bottle of syrup, about a pound and a half, and on the 27th of July the box was full of beautiful comb, having used 121b. of sugar. In feeding, mind and don't spill any of the syrup, and be sure to cover the bottle, so that no bees can get to it, or you will have much .fighting and Bo loose your stock.—J. Lee.

[4621.]—CHLORIDE OF GOLD may be made by dissolving the metal in one part nitric acid by mixing two parts hydrochloric acid.—Nkw Subscriber.

[4621.]—CHLORIDE OF GOLD.—If "Young Photo" mixes one part nitric acid and two porta hydrochloride

aoid in a beaker or bottle and cuts the gold into small pieces will dissolve sooner. Tho deep yellow solution thus obtained yields by evaporation.yellow crystals of the double chloride of gold and hydrogen soluble in water, alcohol, and ether. N.B. Place the dish containing solution of chloride of gold over tho mouth of a pan containing hot water, so as to evaporate the acid off.—Omega

[4621 And 4622.]—CHLORIDE OF GOLD AND NITRATE OF SILVER.—For replies to theso queries see G. E. Davis's letter in this number.

[4622.]—NITRATE OF SILVER.—"Photo" must precipitate all the silver out of his solution by the aid of nydrochloric acid. After standing a day or so, pour the water off, und got a clay crucible and mix the white precipitate (frjin solution) with charcoal and carbonate < f potash, and place the crucible in a well-urged fire. Vou will obtain a pellet of silver, which must be dissolved in nitric acid and solution crystallized in a water bath.—Omega.

[4624.1 —" YOUNG JOBBER."— The selection of a pendulum spring for a watch is regulated according to circumstances, namely—a verge watch requires one kind, a lever watch another kind, tho duplex different again, and the horizontal again differing from the rest. Presuming that he requires a pendulum-spring for the lever watch, proceed aa follows:—Select, or make, a pendulum spring to suit the size required, that is, that tho spring is such diameter that the outer coil lies nicely between the curb-pins and free of the stud when tho eye of the spring is exactly central with the poteuce hole. Lot tho spring contain about twelve to fourteen turns there is uo recognized rule,to determine the length of wire or number of turns chosen by springers. All they have to avoid, concerning this part of the matter, 1b that the turns are not too close to each other, nor too open. A good kind of spring will have its turns the distance apart of four times the thickness of the wire of which it is made; the length of which will very much depend upon the size of the watch. Iu all probability the average length may be Sin. to 6in. Next find by counting the train of wheels—or by the old spring— how many vibrations por minute—or half minute—the balance innat perform, then secure tho spring to the pendulum collet, attach it to the balance, hold the outer end of spring firmly by the tweozers, and while the lower pivot of balance rests slightly on a piece of glass cause the balance to have rapid motion by striking one of its arms, that motion may oontinuo for 90 or 100 seconds, during which time count how many vibrations the balance performs in the time required, say half a minute. Thus tho springer is guided in the selection of a pendulum spring.—Seconds Practical WatchMaker.

[4625.]—FLUORINE.—This element must certainly be reckoned as one among the normal constituents of the human body, though it only exists therein in a very small quantity. It is alway found in the teeth, more especially in the enamel, as well as in bones, particularly fossil ones. It also exists in minute quantity in most animal and vegetable products, in water, both salt and fresh, and in most rocks. There is, consequently, no difficulty in seeing how a supply of this dementis sustained in the human body.—Tkinitrophekic.

[See also G. E. Davis's letter.]

[4627.]—LEATHER DISCOLORATION.—"G. A. G." being in the leather trade, should know that gallic acid, one of the products of tanning, in contact with iron and moisture produces common ink. His moulds and stamps should be made of brass or boxwood.—H. W. Revelev.

[4627.]—DISCOLORATION OF LEATHERiB caused by the iron press. All iron liquors or sulphate of iron will blacken leather. The proper way to make impressions is to get your impression made in white zinc metal, \h\. thick, which should fit in a groove, made to receive it Fig. 1, in the top part of the press, and be

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Fin„z g

fore using it should be taken out and made warm, and then slid back iuto the groove again. Two pieces of fiat white metal, cut at an angle and screwed to the top part of the press^Fig. 2, would make the grooves.—

S. SCHOLKHELD.

[4628.]— INTENSITY COIL.—Inanswerto" W. J. P.," I have made a coil from instructions given by " Dyer," and except that I have made mine only half the size "Dyer " gives, in every other respect I kept to his instructions, and had not the least difficulty whatever. When I connect the coil with two point-cells of a Daniell's battery, the shock is so strong that none of my friendsdare take hold of the handles.—-J. D.

[4629.]—MANGANESE BATTERIES.—I regret that I have, from other business, overlooked two queries in your last issue, in which my name occurs, until now. i have to state that my battery is simply the Leclauche, but without the accumulation.—W. H. Stone.

[4632.]—WEIGHT OF BALL.—Ralph Williams in this query makes it appear that my former answer is characterized by two errors. But 1 am pleased to say that I am not accountable for either of the (apparent) errors. I think that" R. W." himself is accountable for tho first one, and the printer for the other. In the first place "R. W.1' point* out that he thinks I have missed a point (I presume he means a decimal point). If so I beg to point out to him that the said point will be found behind the figure 7 in my former answer, and sot before it, as he, places it, which makes all the difference—7*854 being made to stand as '7854. In the second place the printer has misplaced a decimal point in connection with the weight of wire, *5, or half a pound, being made to appear as Mb. I thought "R. W." would discover the error when he kuew that the weight of the wire was half-apound. He will see that dividing by five and dividing by point live, givo different results. Perhaps a little explanation will assist " R. W." in comprehending the rule (which I hope is not too simple). Of its correctness

I can entertain no doubt after twenty years' almost daily experience. The rule to obtain the weight of round bar iron is as follows: Multiply the square of diameter by 2618, which is tho weight uilbB. of a lineal foot of round iron, lin. diameter. In working out the weight of a foot of jin. round wire for my former answer, I found that it involved several places of decimals, ltherefore took tho weight of a yard, which, coming s» near to half a pound, made the process very simple. On referring to Penn I find that he gives the weight of 8ft. of {in. round iron as '49; Spon gives -51. I take the mean and say -5, which is sufficiently approximate for all practical purposes. Of course I had to multiply tho weight of a foot by three to obtain the weight per yard. Or else (which was more simple) multiply by the weight of a yard of round iron lin. diameter, which is 7*854. I did not attempt to split hairs, as I inferred from " R. W.'s" first query that ho only wanted a rule whereby ho could obtain the weight of round iron in tho shape of round balls and round wire, so I gave tho weights in round numbers. I may now inform "R. W." that the '146 made use of to obtain tho weight of a wrought Iron ball is the weight of a wrought iron ball lin. diameter. So that the cube of any sized round ball multiplied thereby will give the weight in lbs. I think 1 have now said enough in explanation of the rules and the reasons for the rules, and think that if "R. W." will try again (bearing in mind these corrections) he will succeed to his own satisfaction. It is scarcely necessary for me to work the sum now. Rut I do so with pleasure, hoping thereby to satisfy "R. W." Weight of ball7in. diameter.7* x '146 = 60078. Weight of a yard of ^in. round wire -253 x 7"864 = -490,875 For simplicity I take the weight as '5. Therefore

SO

If " R.W." will invest 2s. in a little book published by Charles Fox, Paternoster row, viz., "Peun's Tables," showing the weight of round, square, and fiat iron, brass, copper, I think he would be pleased with the same and find it a cheap two shillings' worth. Does not J. Nash fiud his weight too heavy for a cubic foot of cast iron? Most authors give it as 4501b. This will account for the 31b. difference between my weight and his of a 7in. ball.—Ferhum.

[4684.] — ELECTRIC! CLOCK. — TO " ELECTROMAGNET."—I may add that the clock is equally unoriginal, being a Swiss patent, exhibited iu the last Paris Exhibition. I heard of it from my friend Dr. Grabham, of Earlswood, and procured one through his instrumentality. The English patent has been bought by Mosely, of Covont Garden. The only points to which I wished to draw attention were the mode of making the battery and the remarkable permanence of the action.—W. H. Stone.

[4635.]—CAKE COLOURS.—Procure a small slab and mnil. [ of glass, and grind the powders into a smooth stiff paste with equal parts of isinglass size, and thin gum water; compress into squares as closely as possible, and dry with a very gentle heat. Old crumbling cakecolours, may be powdered very finely iu a biscuit-ware mortar, and sifted through fiue muslin, and ground up as above, omitting the gum water in the medium. If the powders are rubbed up with honey (despumated) to the consistence of thick cream, they answer admirably as moist colours.—Sable.

[4640.]—80UTH KENSINGTON EXAMINATION PAPErtd.—If " J. B. H." sends direct to South Kensington for the examination papers, they will be aeut to him by secretary, Science and Art Department. Ho will have to pay lor them, fid I think.—C. H. W. B.

[4618.]— TWO COINS.—The upper one is a PAXS penny of William I., possibly one of the 12,000 or so louud on the property of a Mr. Dunn, of Beaworth, in Humps hire, in the year 1833. The obverse is PILL ELM REX (William King), and on the reverse is "OCMUND ON Sl'DE," Osmund being the moueyer s name, und Cude the place of coinage, Southwark. The letters PAXS in the angles of the cross, by some, considered to be an abbreviation for "Pax sit," a not improbable expression of hope for peace in the troublous times of the Conqueror (v. Ruding). The lower coin is a sixpence of Philip and Mary, date 1554. Value depends on condition.— T. W. Boouo.

[4650.]— FRENCH LANGUAGE.—I think "Ollendorff's Method" would suit "Patty" very well.—G. W. A.

[4652.]—TONING BATH.—I have used the following for the last four or five years, and know of none superior for rich purple tones:—30grs. acetate of soda, lOoz. water, 5grs. carb. of soda. This to be mixed some hours before wanted, and chloride of gold sufficient to toue the prints in hand added just before required for use. The bath works quickly hot and slowly when cold. I always prefer it hot, and the solution may be used over and over again, ad libitum. I may also add that for the last throe or four years I have always usod nitrate of potash in my sensitizing bath in the proportion of J of silver to 1 of potash, and obtain richer tones and more glossy prints by so doing:—2oz. nitrate of silver, loz. nitrate of potash, 20oz. water, neutralized by a little carb. of soda. I never have any *' old" bath. 1 use it up until there is not sufficient to flout my paper, and thou add fresh.— Unit.

[4653.]—SUNDIALS TO SHOW CLOCK TIME.— Wishing still to leave this problem to your readers' ingenuity for a month, I will only give the querist of p. 574, at present, the information that should ouable him to solve it. 1. Astronomical.—The "Meridian of mean time," or that line in the apparent heavens which contains the place of the sun's centre at every 12 o'clock, may be plotted by attending to the two columns, in any almanac, of equation of time and sun's declination. It has the form of a long italic 8, so leaning across tho true meridian as to touch the northern tropic about Ik minutes (of an hour) west, nod the southern about 1$ minutes east thereof. This leaning slowly increases, and will for many centuries; but the inequality of the two loops is decreasing, having been at its maximum six ceuturies ago, when the 8 was last upright. The leaniug is alternately to the right and left, for about 6,000 years each; but each loop is alternately largest for twice that period; and the southern has been largest ever since Adam's time, when they were last equal. The widest bulge of that loop is now somewhere about 15- of S. declination, and that of the smaller loop, W N. The crossing of the curve on itself is some J minute west of the meridian, and about 10= N • and its four crossings of the meridian are at sonio dk° and 101 N-< at » P0"1' """" near ">e northern tropic, ■ind at one still nearer the southern. I expressly renounced the showing of true clock time for a few days ,>t midsummer and midwinter, namely, when the sun s declination exceeds the last-named two points. I should ,idd that the indications of all dials within half an hour of sunrise and sunset, will always be vitiated by refraction, and the scale should never extend to those hours. 3. Optical.—The solar shadow of every object la bordered by a penumbra, whoso angular width equals the sun's apparent diameter, and the theoretic shadow s boundary (as it would be cast by a star occupying the place of the sun's centre) is half-way between the edge of pure shadow and full light. But while the former of these is always perceptible, the latter never is so with accuracy. Therefore the shadow boundary to be used practically in dials must always be that of pure shadow, which la within, or less than, the theoretic shadow by half the sun's diameter at the time.—E. L. G. -4654.]—OCCULT ATION OF SATURN.—"Hesperus" ill find no difficulty in interpreting the Nautical [tmanac account of this phenomenon if'he'will refer to page 164, where he will find that the horizontal •arallax of tie moon on September 30th is about 59-. This is the maximum amount by which the moon's apparent place in the heavens may be shifted from her place aB supposed to be viewed from the earth's centre. Further, her semi-diameter on September 80th is more than 16V, so that even though Saturn were 75' (i.e. 69' + 16 ) from the moon, supposing both to be viewed from the earth's centre, he would be occulted as seon from some parts of the earth's surface. He is actually about r.6i' from the moon, southwards, at the time of con,unction; so that, as seen from stations having more than a certain northerly latitude, he will be occulted.— 11. A. Proctor. "uly relief; at times the mucous is streaked with blood. 1 bathe the throat and chest with cold water frequently, and have found it a great benefit, but the disease or trouble is never away, and is annoying.—Omega.

[4654.]—OCCULT ATION OF SATURN.—Without examining the Alvmnac, it seems pretty plain that ■Hesperus" must have overlooked the moon't parallax. The elements he quotes, nro doubtless given for •he earth's centre, not Greenwich; and apply to the place where the bodies will be vertical. The Hmanac docs not predict an oocultation there, but at <ireenwich, which is quite possible while their geocentric distance is as great as he states; the moon's horizontal parallax being greater, and Saturn now never much above our horizon.—E. L. G.

[4655.]-MANGANESE BATTERIES.-TO "F.H. B." —T protect my connections from corrosion with a small prate of platinum foil under the copper. I nnderstnnd, however, it is possible to prevent corrosion by making the carbon very long, so as to project some inches from the solution, and painting a thick band of shellac varnish round the projecting part between the fluid and the binding screw.—W. H. Stone.

[4664.]—PRESSURE OF WATER.—The pressure per square inch on the bottom is the same in each case. The pressure of a fluid on the bottom of its containing vessel depends on the depth of the fluid and not on the form of the vessel. "Holbeck " may demonstrate this for himself in the following manner:—Take a plane tube A, and to the bottom fit a water-tight valve, V. This may be pressed up by means of a lever, a 6, as shown in the sketch. F being the fulcrum and w the

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weight. Water must now be carefully poured in till the valve just begins to open and the height of the column of water noted. Now perform the same experiment with a tube of the form shown in the sketch B, the bottom of which has the same area as that of A, and let the valve be pressed upwards by the same, or a similar lever and weight; on pouring water in, the valve will just begin to open when the height of the column is the same as it was in A.—Exhibitioner At Royal College or Science.

[4664.]—PRESSURE OF WATER.—No difference, of course. It iB the most elementary fact in hydrostatics. —E. L G.

[4664.]—PRESSURE OF WATER.—In reply to "Holbeck," the pressure per square inch at the bottom of each pipe is exactly the same, namely, about 5'2a lbs. —thomas J. O'connor.

[4665.]—PROBLEM.—o. Call the regular length of journoy x minutes. The train proceeded regularly CO minutes, then stopped for 30, and had to do the remainder, which would regularly havo taken x— 60, at

three-quarter speed which occupied _ (x — 60)—The

whole took, wo aro told, x + 110 minutes. Hence

(A)90 + 1 (jr — 60) = x + 110. Next, had the train

3 proceeded 90 minutes right,and stopped for 80, it would have had to do what usually takes* 90, at three-quarter

speed, requiring — (x — 90) and these times, we arc told, 3

would have made x + 100. Hence (B) 120 +

3 x 90) = x + 100. Rejecting the figures common, to both sides, equation (A)

becomes -_ (r — 60) = x + 20; and

a. From li + 30+|r-x-L80by merely omitting the 30 common to both sides jx + |j^x + 50, whence

1 r =- 50, and x = 300, as before. So that the f) informa

6

tion is correct, and sufficient alone, with none of u, to

determine that the regular length of journey was five

hours.—E. L. G.

[4668.] —LATHE.—TO "TOMETER."—You ought to be a pretty good jndue of what you are able to do. A great deal more is required in lathe making than a mere knowledge of turning. As to price, the £100 and the £25 lathes are probably each worth abont its price—j>Iu.i profit. You want an amateur's lathe, that is, one fit for a gentleman's use, and seem to think that you can get it somehow at the price of one that an apprentice would be set to work at. Do not, pray, make a 4J lathe: nothing less than 5. I should get the bed cast and planed and fitted on to standard, and fly-wheel and treadle fitted complete as a first start, and I reckon to got that well done will take £11 more or less for a Sin. You can add a leading screw at any time after all the rest is complete, and the bearings for screw may bo cast on or screwed on afterwards as you please. And all the above work I should entrust to Wilkinson, and nobody else. You can get a 5in. lathe of Whit worth with sundry chucks for £90. One of Muir's for less than that, and one of Smith, Beacock, Tannett, for a little more than half Wbitworth's price.—J. K. P.

[4688.]—THE LATHE.—Perhaps ".I. K. P." will pardon me for answering a question addressed to him. I do not think £25 at all an adequate price for a lathe such as "Tometer" describes. If ho wants a good lathe and has not the money handy, he might borrow it, and, as he says his time is his own, he could easily earn the interest of the money advanced, and so gradually payoff the debt.—G. W. A.

[4672.]— KITE.—Tho kite would certainly not act as "W. J." describes, for suppose it to be suspended in the air as he proposes, and to bo inclined at on angle, say of 45', which would be about the proper inclination; then the wind pressing on the inclined kite would act in two ways, it would tend to drive it along horizontllay and it would also tend to drive it up perpendicularly, and as these two forces would bo equal, and supposing there be nothing to oppose or diminish either of them, the utmost tho apparatus could do would be to move in the direction of their resultant, or in other words it would move up from the earth in the direction of the wind at about an angle of 46'. But seeing that the weight of the kite and its appendagos would diminish the force of its upward tendency, and that no opposition whatever would be offered to its horizontal motion, the practical result would be, that though it might possibly rise up into the air, it would, at the same time, move along with the wind at a much more rapid rate. In order that any apparatus may beat up to windward, it is necessary that it Bhould havo something to hold on to, in order to prevent it drifting to leeward. A boat beats up into the wind because its length gives it a firm grip on the water, and a kite will beat up to windward (as indeed all kites do when they rise up from the earth) provided it is held by a Btring to prevent it going with the wind. A kite could no more work up into the wind without being held by a string, or some equivalent contrivance, than a lever could be used without a fulcrum. The apparatus " W. J." describes would drift hopelessly along with the wind.—W.

[4676.]—NITRATE OF SILVER.—Refer to replies to query 4622 in laBt number.—T. W. BooRD.

[4676.]—NITRATE OF SILVER.—The sediment from "Paddy's," salted " slops " is chloride of tilrer. His best plan is to collect the sediment in a large bottle, and when full, Bell it to a chemist, together with R11 his old filter and draining pasBors, or get tho chemist to convert them for him into nitrate.—Unit.

[4678.]—BOURNE ON THE STEAM ENGINE.— In reply to Thomas Watson no better work than "Bourne" is at present puhlished on the steam engine. •' Main and Brown on the Steam Engine " is also a very good work, but it treats principally on the marine engine.—Thomas J. O'connor.

[4689.]—PEDOMETERS.—The motion of the body in walking causes the vibration of a short weighted arm or pendulum which acts upon a small toothed wheel, geared into another connected with the index.—Unit.

[4691.]—POWER OF ENGINE.—According to the rule to which "It. W." refers, the powor of his engine at301b.pressure would bo 4 horse power,thus, 4 1

2 x 2 = 4 -r- 12 = Tn = — h. p. of engine,

hours with the Telescope." can be gathered Iras lie
fact that tho telescope waa or Uic size mezLs ,tl tr
"Turton"—that is, 4in. in aperture Krfilalal
length. I do not recommend the sUaA as artai
figured. The toothed wheel and quadra-ii u-»
expensive; and, again, the letfged part o( tit- st*
should be higher in proportion. The rrm ,jai
quadrant should be replaced by a ■endri-> r.^:
teeth; a cord carried along- the eirctmJ*.***-?: i.
semicircle and making a torn round th* w*&rr. *
the endless screw in my figure, Herring v. ir*i-v
tinuous motion in altitude. In like Qai:^ t z-t
round the circle c, with a turn round th>.a* ir-^.-.
the crown-wheel, would give toe conliSKs iwa
azimuth. The figure is reallyo. pictnrtrs-^rijt
modifications, of a telescope I used ic 'A; &.? A
Marlborough School. The crown wheel liatr.5i
from a part of the appurtenances of a -rasrtoi!
alao filed and set the endless screw, and »----. pet
of work I made of it, more by token. !j **ra
wheel working in the crown-wheel was mad--■ Kxj
breaking a knitting needle into f oar equal a J
tving these (!) parallel to each other rouulaiJ
a rod. The instrument, when tiros eompfcvt »,
singular combination of the expensive and *£»D-ac
place; but the knitting needle and the esi - en
arrangement worked well all the same: asiti^j-z'
of having the two handles, which give LU* ah=. *.
azimuth motions, always in the same fixed £*•"-»
nient position, was such as to rnalce one km si
instrument was an alt-azimuth.—R. A. Pltoc-B.

[4713.]—BEES.]—They will pass inudettw such a hole as you describe, provided yon ccaear entrance of their hive with it in *uch a mii>; - -;

Erevent their escape into the room where the, wi ept. Move them at night, and in the nwrorxv will take the bearings of their new locality beta\ » mencing their labours, so aB-to be able to rind tfceuw. back again. For feeding in winter, nee a syrup m» of white loaf-sugar, boiled down with water, abcsoi pound to a pint.—T. W. Boonn.

[4721.]—FOSSILS.—"H. U." ought most certainly k find some fossils in the locality between Cromer aed Hunstanton. The Tertiary system is very fully developed iu that neighbourhood, and amidst the Crag o! the Pliocene group be mav chance to come upon tbc remains of small mammalia analogous to (he mouse. aliuteeth and bones of placold fishes, and corals, and -tieils of innumerable species; marine plant* are likewise to be found. The strata consist of marine and L-co»fruie deposits of shelly beds of snnd, clar. and velA-'w ktam. and flinty shingle, generally resting on the chxJk *r?1em. ••H. 1." should wander into anr gravel pits or »m», &c„ and closely scrutinize c<ery rock near wfcirti he comes; he should also provide himself with a ha-nraer for the purpose of detaching seeci-neiis. The chalk er Cretaceous system liea inwudiaUlj \pe\owth* Twttarv. and is rich in shells.—Abthi-u Vs.ui.aauA

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therefore three times the given pressure, or 901b. per sq. in. would be necessary to enable the engine to work up to 1 horse power. With respect to the thickness of boiler plate, I must refer "R. W." to some practical boilermaker, whose advice will be safer than mine, for 901b. is an nnUBUally high pressure. If possible, it would be far better to use an engine with a 8in. cylinder, since then, the pressure need not be more than 401b., the expense of boiler being, of course, proportionately reduced.—Veu

TrMNUS.

[4698.]—BICHROMATE BATTERY.—The plates are usually about ijin. or 4in. between the faces. The resistance of the solution is so small that 1 think very little powder would be lost, and greater constancy be obtained, if they were lin. apart. The plan for connecting (given nnder the heads of "Carbons'' and this battery iu my papers) is the best possible—viz., electrotyping the top of the plate and soldering.—Sioha.

[4701.]—CLEANING COINS.—Caustic ammonia will olean silver coins. Much more harm than good is likely to result from attempting to clean coins of any value.— T. W. Boord. ,

[4706.]—PHOTOGRAPHY.—"In a Fix " has overdosed his washings with salt. A vera small quantity of talt is sufficient; too much undoes it all. "In a Fix " hu*l bcttcr put all his future washings into another mug and try to precipitate tho silver by adding a little of the ovcr-ealted washings to it instead of salt, and Bo gradually use it up. Unit.

[4709.]—PROCTOR'S TELESCOPE STAND.—Tho dimensions of the stand figured at p. 17 of my "Half

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[4731.] REMOVINCJ WRINKLES FROM PRINTS.— Will a brother subscriber inform me how I can remove wrinkles out of a coloured print? The print is fastened to the back of tho frame with gum or some other adhesive substance, but in places it is drawn from the back and rose up in wrinkles.—Winner.

[4.783.) PEARL OYSTER-SHELLS.—Can any one tell me where the above are to be purchased and the price? —Thos. Fletcher.

[478fi.] BALANCE IN VERGE WATCHES. — Will any of our watchmaking brothers enlighten one desirous of gaining knowledge as to the best way of uprighting the balance in vergo watches when the cock and potence holes are worn and want refilling, or have been refilled, and left with balance leaning on ono side? What I want is the bost and easiest method of setting out the holes ao that tbey shall be perfectly perpendicular, as I And frequently that watches which havo been so repairod fail in this essential point.—Cheek-Ache.

[4737] BLOWPIPE.—I wiahfor someinformation upon the practical use of the blowpipe. I possess one luin. in length;of brass, and can manage to braze aniall articles such as watch hands, &c, but when I attempt to Bolder new joint or pendant on watch case with silver solder it results in a miserable failure. I use a common tallow caudle, or in place of which I use a small benzine lamp filled with benzoline. Then I place a little powdered borax on the joint, or whatever it may be, with the silver solder on tho top, then placing the article in lny leit hand I direct the blowpipe and flame with my right hand upon the work, and blow till the boras is nielied and the silver also, which has been laid on in a strip, which runs into a small round globule glittering and dancing beneath the heat of tho flame. This is all that I can attain. The fault appears to be that I cannot obtain sufficient heat in the article to be brazed to enable it to take the solder (but I may be wrong), although I may blow till my cheeks ache and my eyesstart. Is tho fault in the blowpipe, the candle, or lamp, or want of oxygon in the breath, or where is it? I know that snch work is done daily, and hope to receive instruction through your columns.—£he£k-achb.

[4788.] GEOLOGICAL.—There is a matter which has puzzled me much, viz., tho "cause " of the intervening strata, or the sandstone rocks, which is found between the different coal bods. In other words, if the vegetation of the coal bed periods has been caused by the heat

of the Bun and seasons, what has been tho "cause" of

the sandstone periods V—Veritas.

[4739.]-COLOURING SIZE.-As no correspondent has answered inv query, 4317, page 430, can any one tell "¥> w.h'« ,to Put >Qt0 tho size to make it a very pale blue as I find by putting indigo into tho size it makes it a green?—John Bury.

[4740.]-CONTACT BREAKERS.-Will "Sigma," or somo fellow reader, describe the contact breaker of the largo coUnt the PolytecUnio (or any other) that counteracts the destructive action of tho spark ?—R. N.

[4741.] - DISSOLVING INDIA-RUBBER. _ Would someone inform mo how to dissolve india-rubber, so that it ww mix with oil and turpentine ?—Robber.

[4742.]-STEREOTYPING IN A SMALL WAT-I hnve had many attempts at stereotyping in a small winboth bv tho paper and plaster of Paris procesaos, but have always partially failed. Having read, here and there, about eleotrotyping, I have thought of trying that process, and now wish to know whether, by taking an impression in gutta-percha or plaster of Paris, I could get a slight deposit of copper upon either of them sufficient to print from. After having obtained the battery, la the process-more difficult or open to failure than stereotyping? What would be about the price of a battery sufficiently powerful to coat a surface of, say 7in. by 4m. of mn.c stereo, which I have obtainod bv a new process, and dc-ire to prove r I should feel greatly SSTefSrS^ nUmer°nS «—pondentsgwoul5

[««l - HEM-STITCHING MACHINE.-Can any

"nij^T,^7"1'0"?^00^ to th0 construction of the hem-at toning machine, or how I may get to aoo the specification of the patent ?-AquiLLus

n ft74H-aUN-C1?TT?NWU1 »»y k'°d reader of our paper inform me how the above is made 1 I have tried equal parta or nitric and aulphuric acid ; poured over cotton woo , it turned a brownish colour, and some be came like jeUy, and after a thorough washing failed to he explosive 1—Experimentalist. ^^

W4?-]-STARCH.-What substance oan be used on collars, Ac, in shops ?—Tidy.

[4746.1-SCREW CUTTING. 1 ahouldbe very glad

tS", VUd """Pendent "J.K.P." would give me MM information on tho screw-cutting lathe I have SiTM °°' lath,! w,th bMk *ear ttnd «»de rest, the bed "«ddlr l„8S?1\Jli,3Irdm''rT serew-cutting lathes, and liewl»M?a .wh«tlw,"»'to I"-"* is what form of nut donot^aof?*°m^VVJ?emgonl'r,ln amateur, I or the7X\f°.mI,1«!»ted»«Hir. I have had a screw cut thread \V '„1h h"" ?"■' ,or *l ,The Pitch " *in' siuare nut with Kevfi I .1S° m° '° haTM a 3PHt nut « s°"<l front? is.eh.r'l t0 WC"k With hin<Uo ttt «" 'ton on the ht *"!ft* eent flome usc,ul to'ormat„ *„ mi \ tbe' which encourages me to ask him

[4748.] - ELECTRO-MAGNETIC BATTERY.—Will aome kind reader inform me how to construct the above so as to produce a strong magnotic current? any valuable hints will be acceptable.— Beriro.

[4749.]-CARBOLINE.-Wonld "C. D. C." be kind enough to state where I can obtain carboline and at what price per gallon ?—A. J. Jabman.

[4750.]—SOFTENING AND PURIFYING WATER — I should be glad U somo correspondent could tell iue where I could get a description of " Clark's patent for softening and purifying water," as mentioned by Dr Frsnkland in his report to the Registrar-General for the

TM°n ,?i^aly\„a,nd,re'crred to m >our "umber for August 19th, p. 182.—J. c.

[4761.]-TAPS AND DIES.-In the English MeChanic for August 6, W. Reed asks (4434) "if he can make left-handed taps und dies from a set of taps and dies for right-handed work," and on the 19th "Semper Paratus' replies that he can; "he has only to work them the other way or backwards." Will " Semper Paratus please say if he has succeeded In producing serviceable tools by this moans alone '—T W

BooRD.

[4752.]-DIFFERENTIAL CALCULUS.-Will some ~ >l»»meliowtodothiBgum? It isin >■ Woolhouse's Differential Calculus," p. 27;

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[4758.J-GERANIUMPROPAGATION.-WU1 a brother reader give me a few hinta how to alip these plants and whether or not I am to pnt anything to tho bottoms of the slips ?—J. E. Clat.

[4754.]—DRESSING SKINS.—Will any reader kindly inform mo how I can dress into mats such skins as sheen doer, and dog ?—Taweb.

[4755.]-CONICAL WINDING DRUMS.-Will aome brother reader kindly give some particulars respecting tho construction and working of conical or spiral druma aa applied at collieries for drawing coals, and state what oonditions are to bo observed in order to ensure their safe working ?—W. M.

[4756.J-CONSTRUCTING MAGIC-LANTERNS.—Can any of your numerous readers inform me how to construct a magic lantern; where the lenses may bo procured, the prices of such, or how to grind tliein; nnd material required for such purposes ?—A. Storment.

[4757.]—GAS PRESSURE GAUGE.—Will any one give me an explanation of a gas pressure gauge?—Alex Ogilvie.

[4768]-FRESHWATER FISH AND FISHING — Being an ardent follower of "Old Izaak" and "the yentU craft," I always road with interest "A. T.'s " replies to questions. Can he inform me of any places near London where good fishing can be had on payment of a small fee; or where permission can be obtained on writing for the same? Tho groat drawback we workers in town have is the difficulty of finding spots noar at hand where, in our few hours stolen from toil, we can seek recreation at once harmleBS, healthy, and amusing —Piscator.

[4759] .—POLISHING W ALKING-STICK8, Etc.—wa1 any of our numoroua contributors kindly tell an amateur the beat polish to uae for walking-sticka, umbrella-sticks, &c tWhitethorn.

[4760.]-EXPANSION OF STEAM.-l In Spon'a • Dictionary of Engineering" under this heod, page 428 (articlo "Boiler"), it is stated that "the dual logarithm of a given number can bo calculated without the use of tables in a few niinute8." Aa my table of hyperboUo logarithms goes only to the number of ten I should be glad, having to calculate the mean pressure of steam corresponding to a ratio of expansion of 1 to 17-47, to have the rule as to dual logarithms explained so as to be able to employ it (?) for any ratio of expansion. 2. Not being up in logarithms, would auv kind brother reader give me a table of hyperbolic logarithms of numbers from ten upwards to twenty, and also explain how the hyperbolic logarithm ofa nnmber and fraction (or decimal fraction) of a number between uuits and fractions of units in table is determined. Example Let the number bo 470. Tho next lower number in table la 4S0 (4}), for which the hyperbolic logarithm 1-5040774 stands, and the next higher, 475 (4j) for which the hyperbohc logarithm 1-5681446. I want to know how 1 am to find the hyporbolic logarithm of No. 470. 8 What la the rule for finding the end or ultimate pressure of steam (not tho moan) for any given degree of expansion? Does the pressure decrease exactly in proportion to tho increase of volume ?—A. W. E.

[4761.]-SLIDING RULE.-I wish to know how the scales, or rather the divisions, are laid down, thot is sot out on tho sliding rule, for working proportions areaa, diviaiona, &c. Information will greatly oblice —robert Bridoabt.

[4762.]-DISPLACEMENT OF SHIPS.-Would Mr W. lelton give a sketch of his model, and how it is divided, for computing tho displacement of ships? Aa models are generally made of wood, will the rulo hold good for iron ships ?—G. B. D.

.. I««S.]-SOLDEBING BRITANNIA METAL.-Now

J-B h, having examiucd the recipe u* described

by ■ SergiiiB," cannot understand the composition of hell metal, thinks it may do very we'll for iron and braaa but ia afraid to use it for Britannia metal. The latter belne ao soft, whilst bell metal so hard. '■ Sergius's" reply would oblige.—J. B h.

[4764.]-BRONZINOCOPPERURNS.-Can envoi vour many readers inform mc of a simple way of bronzing nrns for hot water, chiefly used on the tea-table, value about *5 each, colour very dark copper colour.—J. B h.

[4765.]-PISTON AND PRESSURE.-A repreaents a cast iron cyhndor fastened to the piston-road as shown, and working thr#u«h tho bottom of the steam cylinder in the aamo manner as an ordinary horizontal Jn-rine I wdl suppose the engine to be an expansive ono Now in my plan the piston, having its full snrfaco exposed to the steam, must, when the ports are open, have the same pressure on it as though the cylinder A wore omitted Ho far all rLjht, but wueu it (the steam) ia out off will

cylinder A? I think it will, because of tho piston allowing ita full area to receive the pressure; but would like to know if there are any rules to determine the force of my argument.—One.

[4766.]-STAUNCHING TIMBER JOINTS.-I would feel much obhged by any reader informing mo as to tho best material for staunching tho joints of a canoe (timber-built, of course). Is marine glue used for the purpose, and if so, how prepared for uao ?—Ant Ares.

[4767.]--MODEL PADDLE-STEAMER.-I am making a model ateamer (paddle), about 7ft. long, and wish to fit air compartments to prevent immersion; will some kind r5?_TMln/orm *"* how t0 du ''■ TMd wlm' to make them

[4768.]-POLISHING PLA8TER OF PARIS.-Would you or some of your numerous readers inform me how to polish plaster of Paris ?—A Two Years' Subscriber.

[4709.]-CIVIL SERVICE EXAMINATIONS.-Can any reader give mo information respecting iho alteration in the Civil Service? Why tho examination is done away with, and whnt course of study it involves? I shall feel much obliged for any information on the subject — J. M. C.

[4770.]-FIXING PRINTS ON CARDBOARD.-I have a quantity of prints I wiah to affix on to cardboard, and should be obliged if any of your readora would favour me with a recipe for a paste or cement for fixing them and the bost method of doing so.—T. E.

[4771.]— FLUX FOR BRASS, GUN-METAL &a -Will some kind reader inform mo what flux ia uaed for brass gun-metal, Ac, and how? In running tho metal into a' mould I find it leaves a crust hanging from the crucible, and however smooth the mould may bo it turns apongy and not solid, therefore very often of no use. Tho flux' I think, clears it in a great measure.—Lilliputian.

[4772.]—HERB BEER.—Will some reader of the Enolish Mechanic givo mo a receipt for making cheap horb beer?—Anxious.

[4778.]—CAUSE OF THE EARTH'S REVOLUTION. Can you givo me any idea what causea our earth to revolyo? I can underatand it being set in motion, bnt why does it go on, as far as we can judge, at the same rate for at least thousands of years? Call me. if you like —A Moke.

[4774.]-THE AILANTHUS.-WU1 some of your correspondents kindly give me aome particulars of 'the Ailanthus silkworm? I wiah to breed a few. 1. When does the egg hatch? 2. How long before the larva becomes a chrysalis? 3. When does a chrvaalis hatch ?J 4. Where Is tho plant to bo procured upon which it feeds? 5. «i hero can I procure aome egga? I have aoeu the names of other Bilkwornis but do not know where to look for them, but shall bo glad to have particulars of one or two of them also—A Constant Reaper.

, [4775.] -LUMPS ON HORSES.-Will any of your readers kindly inform what they consider the best cure for small lumps on horses, commonly known as "heat weals," and what to apply when they break under the collar ?—A Groom.

[477C.]— LATHE.—Your correspondent T. W. Boord, gives the numbers on tho division platos of lathe, by different makers. It would interest many to know tho size and pitch of the acrews on the respective mandrels and whether the same gauge is adapted for " ornamental lathes as for those for general use ; also the diameter of the dividing wheels and pulleys of each lathe. I presume tho lathesreforred to are Sin. centre.—Ajiatelr Turner.

[4777.]—LINK MOTION.—I am aurpriaed to eeo "R. Vi. B'a" queation (4581), after the very clear and intelligible pupera by Mr. Baakerville on the aubject May I asli Mr. Baskerville to explain a aentence in the last paragraph but ono in liia laBt letter about the stationary link as applied to the locomotive? He savs it requires " a length altogether out of the question in" a acrew engine or a locomotive." To what extent tho word properly applies I know not, but there are a largo number of engines running on the London and NorthWeatern, and London, Tilburv, and Southend Railwavs with this motion.—G. W. A.

[4778.]—DENTISTS' CEMENT—Can some one inform me how the cement that dentists use in fixing tho teeth in the metal is made?—X. L.

[4779.]— HOLTZ'S ELECTRICAL MACHINE.—Will "Sigma," or any othor correspondent give a description of Holtz't electrical machine, or state in what work English or French, tho aamo may be obtained? —A Revenue Officer.

[4780.]-TEMPEKING STEEL NEEDLE WIRE — Will any one inform a brother reader how to harden and tompor line Bteol needle wire iu 80 or 40in. lengths 1 An Old Subscriber.

[4781.]-SUSTAINING BATTERY.-Could "Sigma" or any other electrical reader give me a description of the battery uaed for working Tyer'a railway block ilmlilT It has been described to mo aa a box containing eighteen atcneware cell.!, and at the bottom of each cell there ia something very bright like mercury, thia is all the information I could gain on the subject. I am very anxious to learn what this battery Is, and how long it will remain in action.—Code.

[4783.1—TOMATO SAUCE.—Can any reader give me a simple recipe for making tho above sauce ?—Bon Vivant.

[4783.]—CONVEYANCE OF WATER.—How much power can be utilized from a supply of water conveyed laO yards in ljin. piping with a fall of 12ft? What is the best means of g uning that object,—combining tho attainment of tho greatest percontii^o ol power with sun

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