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balls, or other light substance«?, the other, alter cleaning the grain from remaining impurities alter being scoured (each acting independently of the other), depositing two kinds of screenings, one taken from the wheat before it i* scoured, the other after, und both cleansed from doit and chaff, and ready for market. The scourer is oonatroeted ou the smooth surface principle, and therefore is not liable to break tho wheat, which is a great drawback to rough surface machines. If ordered they attach a shaking shoe, as seen in cut No. 1, tho iirst «creen of which is for the purpose of carrying off any impurities larger than the grains of wheat. The second screen sepáralos the sand, seeds, Ac. With this shoe the machine forms a complete grain cleaner of itself. With regard to fixed v, balance rhynds I should think i he increasing scarcity of the fixed rhynda will be answer enough, being almost entirely superseded by the J lance.—Seroius-Î

[4409.] — FOUL AIR.—It is a most mischievous error tu suppose that wherever a light will burn a man oan live. A candle would burn to its end in pleuty of g iseous mixtures that would be instant death to any wirm-blooded animal entering thorn. No man should b¿ allowed to descend into a well, a liquor-vat, or any P ace left for many hours without downward outlet, till a bird in a cage ha« been lowered for вошо minutes and drawn up alive. Tho only reason why ascending into an uutried upward well, or place without upward outlet, i * less dangerous than descending an untried downward receptacle, is because light gases have a far more active diffusive power than heavy ones. It is provident ial that carbonic acid, tho commonest by far of all irrespirable ones, is heavier than air of the same temperature, but comes from all its ordinary sources, as animals' luugs and combustion, heated enough to rise at first. The above accidents arise from tho comparatively rare cases where it is produced cold. The ordinary warm r-irbonic acid, nearly as fast as it can accumulate against j >ofa or ceilings, must cool and descend, во as to be quickly spread and diluted. Still, no lantern, from a lighthouse to a policeman's bull's-eye, is made without perfect upward drainage, for its continual outflow. Indeed, every lantern maker knows that not one would be saleable without it. No par'icle of air can enter any lantern twiee. In all our dwellings, on the contrary, Lud most public buildings, the ceilings are the most perfect arrangements that could possibly be contrived for retaining and forcing all foul air to be breathed -ver and over attain as manv times as possible.— E.L. G.

L4415.J— CURIOUS PROBLEM. —According to tho ■answers received from various sources it would uppear tliat an "irresistible" force cannot co-exist with au 'immovable" body and vice versa: in other words, theso lerms are incorrect, and as definitions of things which have no existence should bo crossed out of tho dictionary, or at all events become obsolete. To avoid such a conclusion my alter «jo suggests that an "irresistible" force coming iuto contact with an "immovable" object would " make a hole through it !"— Saul Rymka.

[4474.]— HORSE POWER.—" Vertuninus" (p. 548), tfives to my mind rather a curious rule for finding the uorse power of a cylinder. May I ask him if the stroke is not worthy of some little consideration. To illustrate tins I will take his example, viz., a 6ln. cylinder; it may have 9in. stroke as in a locomotive or 4Un. as in a screw engine, and by Ыз rule the two cylinders are of exactly : he same power, whereas in reality the 9in. is exactly 'louble the power of the other.—G. W. A.

14481]—THE BAROMETER " DIFFICULTY."—I was aware that standard barometers have a movable scale ending downwards in the point mentioned by " A. M. \V." (p. 571), and by thus separately measuring the difference of level at every reading, wo eliminate the effects of any inequality of bore in different parts of tho tubo or '•istorn. But if thie is expected to be done with every barometer, as "Exhibitioner at Royal College of

Science" implies (p. 548), 1 call it a most "clumsy" expedient, not meauing by that term inaccurate but inartificial, or in the sense that we call it clumsy of Chinese watercarriers to inherit the contrivance of a yoke to which they append a bucket of water at one end and a stone 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 tho present level of mercury in a simple rigid cistern, and В in the tube, Win. higher. Suppose the surface A to be nine times the area of B. Then if the top were opened, both surfaces would come to the level C, three inches aboye A. Now, if the makers expect moto bring "the fluid in the cistern always to the same level when an observation is made," I beg to tell them and "Exhibitioner,"

I prefer tho lees troublesomo course of obliterating their scale, and making a directly usable one, by dividing the 27in. from С to В intoSO nominal or scale inches; in short, figuring every 9-10 of an inch above or below В as an inch. If they object that the tube n cistern are not parallel - sided, I say tin v ought to have been so practically and th*4 their not being so is most "clumsy."—E, L. G.

Г 4-1840 — BUNSEN'S BATTERY.—"An ОЫ Subscriber" will find the easiest modo for cutting his carbons is to fix hU carbon in a vice and cut it down with a handsaw. The saw will cut about twelve, then will require re-sharpening.—A. J. Jaiislak.

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

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

[4504.] —ELLIPSES.—Tho common trammel (or elliptical compass) has been described and figured several times in the English Mechanic, better than by T. W. Board inthis number (p. 548). Thus, in vol. VII. alone, I find it rightly figured by " Novice Barnsley," p. 19ÍI, as well as the still simpler mode of striking ellipses by foci and cord, three timen given, т»р. 148, 149, 314 ; and a third method on a wholly different principle, p. 452. Moreover the "connecting-rod" oval that our present

II J. K. P." patronizes, is there also confounded with an ellipse, or an" ellipse in perspective," pp. 237, 323, and its first introducer, Thomas Arnall, even calls his instrument for striking it an "elliptograph." "J. K. P." must surely see that if it be erer egg-shaped, it must always be unsymmetrial and a more complex curve than tho ellipse, however, long his connecting rod. In fact, it Is an oval of the fourth order, while ellipses and all conic sections are of the second, the samo order as a circle. T. W. Boord's figure of the trammel has been made puzzling by the printer inverting it, but is also wrong by having the arms of tho cross unequal; and an attempt to disguise the inherent defect of that instrument which is, that owing to equal length of grooves being required each way, you caunot 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 long as twice its width. In fact, only ellipses of small eccentricity can be drawn by it, and thu larger the loss elliptic, by suppressing one arm, however, or rather halving the entire cross, we can draw any ellipses not exceeding its width, however narrow, by half at a tune. "J. K. P." says this is necessary with Cowper's Ellipsograph, which'I do not know. I greatly doubt the possibility (without very complex machinery) of striking any of more than small excentricity with ink and a drawingpen; though it is perfectly еачу with pencil. The drawing-peu introduces difficulties that I long ago, though constantly drawing ellipses, decided to regard as not worth solving.—E. L. G.

[4511.]—WEIGHT OF BALL.—Tho length of wire that can be drawn out of a ball of iron, may be found without reference to the weight, by dividing twice the cube of the diameter of the ball by three times tho square of the diameter of the wire. If diameter of ball is 7", and diameter of wire ¿", wo have

2 x 7* 2x7x7x7 length of wire = a x ¡gj - 3 x Щ

_ 2x7x7 x 7 x 16

3 = 3658;$in. = 304ft. lOjjin. The weight of an iron ball may bo ascertained by multiplying the cube of the diameterin iuche-* by -136 for caet iron, and by 146 for wrought-irou. These foctors are obtained by multiplying '6386,the constant used in obtaining the cubic contents of ball, by -26 and '28 the weight of a cubicinch of cast and wrought-iron respectively.— William Moon, jun.

[4515.J—FELT HATS.—I cleaned my felt hat with spirits of turpentino and a soft sponge, and by rubbing gently with the grain of the felt.—Aquillus.


was doubtless occasioned by a current of hot air rising

from the roof.—Unit.

1519.] — PHOTOGRAPHY. — Ordinary shellac dis solved in spirits of wine makes a good and cheap negative varnish, to be poured on to the warmed plate the same as collodion. Or tho hard spirit varnibh, mudt for carriage painters, diluted with twiee its quantity »t 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 iuto pieces. Then place it on tho strainer, when it will drain into the pan beneath perfectly clear. This is the most simple and the most perfect plan I know of.—Winner.

[4535.]—HORTICULTURAL.—"G. H." in pruning gooseberry and currant bushes must be guided by the strength of the soil. At any rate, all main branches that crowd one another should lie thinned out, and only as many left as the 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.—Saul Rymea.

[4539.1—CHIMNEYS.—In reply to the inquiry of Mr. Moody in your journal of the 19th inst. (query 4539), I beg to give him below the principal dimensions of a vory < legant 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. The foundation is .:'■' ït._ deep, forming an equalfour equal-sided prism of 14ft. 8in. side. The plinth is 19ft. Hin. high by lieft, side. Tho shaft is 92ft. high from top of plinth, so that the total height from ground-level is 111ft. 8in. The width of Hue at base is 59in., and at top 89Jiu. The thickness of masonry in plinth is 39Ain. and in the ehaft at lower end 29jin.¡and at top 10. Plinth and shaft is cagped with hewn freestone. The canal from boilers leading into base of chimney is immediately under ground-level, and is 5ft. 6in. high by 4ít. lin. wide.—E. W. A., Cologne.

[4541.]— EMBROIDERING MACHINE,—There is a machine special for this, but very dear. There are attachments for the same purpose to some makes of "Wheeler & Wilson," also to " Singer's," and perhaps the "Weed," and the "Howe." Bradbury's W. W. makes, so I understand, six different stitches; ranging from single thread chain stitch to eight thread embroidery. Seller's W. W. uses up iofive thread embroidery stitch. I consider the "Gulph" treadle tho host chain stitch machine. Perhaps it would suit "A Braider," but chain stitch is ¡wt embroidery stitch.— Aquillus.

[4545.]—SECRET CODES.—In compliance with the request of "Argus," I send you tho clue to the " secret code" upon which I commented in your columns in No. 378. To take the simplest case, let us suppose that the suspected word 1я the first in the cipher, and is believed to be BEACH ; tho corresponding letters in the cryptograph being ULOTU.—We proceed as follows :—1st. Write down tho alphabet in order as far as the lowest letter in.tbe word—i.e., as far as H—and draw under it as many parallel lines as in the suspected word. und. On the first line place V under B, on tho second L under E, on the third О under A, on the fourth T under C, and on the last U under H—i.e., the cypher letters, one In each line, under the suspected letters. 3rd. Complete theso lines in retrogradealphabctical order towards the left as far as the column under A, and the first column gives tho key. Thus ABCDEFGH&c.

H I J К L Ac
О *c.
R 8 T éc

N О V Q R 8 T U Лес. Showing tho key-word to bo THORN. In the second case, suppose that the word is not the first, or that the sentence begins " The beach." Our first, second, and third trial will fail, but the fourth will produce this resultcipher being SRTJV—


R8 . . .



H I J ... .


which gives RNTHO as key-word, which by an easy transposition becomes THORN. If the known word be longer than the key-word, tho latter will repeat itself, thus THORNTHO; if shorter, we must guess at the rest of the кет, but ice ean always obtain a$ manyeontecutive Ufan of the key a* there are in the known word. I may be told that this plan is Blow when the word is contained in a long sentence, and that it may be defeated by using askey a set of lotters having no meaning. To tho first I reply that my object is only to show that with patience the code is not secret; to the second, that no unconnected series of letters can be rctaiued in the mind long with certainty, and that if a note be made of them, security, the great merit of the system, is lost, as the word may fall into the hands of others. Allow me to add that I have invented a little instrument which enables any one to write cryptographs almost at the rato of ordinary writing, and to read them without putting pen to paper, of which, if the subject still retains iuterest, I will send a sketch, with full permission for auy one to mako for private use, or for sale, as I am merely acting en amateur in tho matter. And as I have taken upon myself to disclose the secrets of other plans, I beg to subjoin two very short specimens far practice—the one founded on the principio that I have tried to elucidate, the other upon the same principle, with a modification which I have introduced. I may aay that the keyword in each if a very common word, and I will graut that the word JONES occurs in both. If any brother cryptographer on discovering my plan will kindly communicate his method ho will oblige mo and doubtless interest your readers. I should add that in neither cryptogram have I transposed the alphabet, omitted any letters, or introduced signs without meaning, all of which methods require two copies to bo kept, a fatal objection—

1st Cryptogram 2nd Improved Do.

YMNSAUMJSHOXSYG KUOPFCyASMTLGPFYUL To conclude (or the prr-ont, as an old rhyme says, а perfect cryptogram should be

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

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

[4506.]— 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 "Mus" is inquiring about.— Unit.

[4559.1— HORSE-POWER OF BOILERS.—Find the area of water surface freely exposed for the evolution of steam by multiplying the length of the boiler by the length of surface line, measured across the glass gauge, which in this case should be at least 6it.; divide this product by 4*78 square feet for the horse power.

Consequently -aq— - 40*78 H.P.

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

401b. inch, is «.tfcmT = l0**1^ 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 boilors;


28 cube feet,

allowing 1 cube foot of water to each square foot of furnace, 28 will also represent the area of furnace in square feet. Therefore, the relative volume of 401b. steam being = 500, we have 28 x 500 =.14000 cube feet of steam per hour. . 14000 Consequently йр^'л) ■» 3'9 cube feet per second.

and 39 x 10*46 = 40 78 H.P. also.—B. D.

[See also letter headed "Boiler Power" in this number.j

[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-irou by 3*3 for iron, and by 3*4 if for eteel, which will give him the weight of a lineal foot in pounds, and multiplying that by the length of the rail in feet will give 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 months, 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 good paint'! 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 h у tiro-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 edge of a long narrow strip of Silurian rock■*; 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 I presume " M. M." refers to its odour, that may at timos vary, being dependent upon its rectification and the heat at which it was originally distilled. The wood spirit must be obtained from the revenue stores.—A Revenue Offices.

[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 BRASSWORK.—The inside tubes of microscopes are blackened with a mixture of lampblack and turpentine, applied with a soft brush.— Medicus.

[4576.]—BLACK BRASSWORK OF MICROSCOPE. —Vegetable black mixed with lacquer aud 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 the power of the two batteries, I cannot satisfactorily answer "Northumberland Subscriber."— A. J. J Arman.

[4582.]—GOLD LEAF.—"Chemicus" should buy а book of gold leaf, when he 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. Reveley.

[4582.]—GOLD LEAF.—To prepare a book of leaf for use out of doors, take a large pair of scissor» and cut the back of the book right off as near the sewing as convenient. Then take up the top leaf of paper and rub the sido that was next the gold on the face or hair; lay it down again on its leaf •£ gold; pass the hand over it

smoothly and with moderate pressure, and the gold will be found to adhere sufficiently ; then lay it aside, gold side up; do the same with the 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 points 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,—Worein о Woman.

[4588.]— TELESCOPE.—Varnishing the inside nf the 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 waeh his feet every other day in warm solution of common salt, and ho would not complain of tender feet.—MedíCus.

[458.).]-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 «commend "Factory Lad " and all who wish to grow plants indoors, under the circumstances he describes, to try some of the Sedum and Echevcria, or perhaps he will understand better if I say Stonecrop and Houseleek tribes. They are very interesting little plants, and there are many beautiful verities bearing red, white, aud yellow flowers. Their habit is very dwarf and compact, seldom more than 6iu. from the 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 soil, 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, eorydalis, 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 poet 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 homo counties, in which case ho must let me know the 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 pure, but dissolves, in water and alcohol with a most intens« light nfln colour. It poesesaes a$very bitter taste, and h* a tonic If present in beer it may be detected by evaporating ют.■ of the liquor considerably, adding a few drops of dilate sulphuric acid and filtering. In the filtrate soak a fe« fibres of clean silk or wool for some time. If they th*n present a canary-yellow hue, the presence of the atid may be considered a* demonstrated, but a mereja brownish colouration should be disregarded. I may «vd d that picric acid is prepared on a largo scale for silk »id wool dyeing, and costs about 3s. per pound. It i- by some authorities stated to act as a neurotic puison.— Trinitrophenic.

Г4605.]— PROPELLING A VESSEL BY A WINDMILL,—Mr. Burton does not seem to know that the visionary project of propelling a vessel head to wind Ът means of a windmill on board U a scheme of тест ancient date. If Mr. Burton objects to ordinary okilA he may adopt a kite provided with the necessary ax^ равнее for striking, in order to bring it down and with guide-lines, in order to «ail as ships do within five point з of the wind's eye. A kite of equal power does not require one-fourth of the canvas used in common sail—H. W. Reveley.

[4605.]—PROPELLING A VESSEL BY A WINDMILL.—I beg to inform Thomas C. Burton that nine years ago I made a model of a windmill for working both screw and paddle wheels, and tried it upon а Д boat, and found it to answer admirably. It would ко straight ahead against wind or tide, but I then saw that I could make many improvements in it, and I now have a working model, made upon my improved plan, which I could guarantee would go double the speed of any sailing vessel. It is very easily managed. One man can sit and steer, and have entire control over it; can stop here, go ahead or astern, without the least difficulty When not required for use it may be left, as it would be perfectly safe, and a gale of wind would not have the least effect on it.—John James.

[4607.1 -ORGAN BUILDING.-Stop diapason pipe* are made louder by giving them more wind through the foot hole. If that does not produce tone enough take off the cap. and with a file open the wind-way a little Possibly the mouth of the pipe may also require cutting —R1 WD brass-wire is usually used for springs?

[4609.]—AIR-CANE.—The drawing on p. ■No does not show the stop preventing the tumbler from turning further than necessary to free the sear; the trig"espring is planted the wrong way, and the mainspring is not drawn sufficiently high to allow lor the traverse ol the tumbler. An air-cane is straight, measuring about ML 2m. in length, and unscrewing in the middle, as shown ш the accompanying sketches, which are the proper sizes for a very large one. A A, lock plate; B,


[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.—Reveley.

[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 in the pot, boil it, and then it is ready for use.—A. S Torment.

[4602.]—MELTING GLUE.—If " S. N. R." will break up his glue in small pieces, put it in his glue-pot with a little more water than will cover the glue, thon 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 freo on the wood. Add a little water each time he melts it.— J. G.

[4602.]—MELTING GLUE.—The proper way to melt glue is to put cold water sufficient to cover it and when softened boil in the glue-pot; of course if it is kept melted long it will want more water added to it, on account ofey&poration.—R. N.

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

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

[4001.] —PICRIC ACID.—TO " S. H. B."—Picric acid is made by dissolving indigo in email pieces in ten or twelve times its weight of nitric acid, sp. gr. 1-43. When all tho 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, ami 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, aud used by dyers to give a beautiful green colour to cloth.—Omega.

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

barrel; C, ballet; D, ah* way; E E, socket of striking pin, shown separately at F; G G, end view of lock. showing entrance of air-way and end of striking pin; H H, section of breech piece, containing the only valve belonging to an air-cane; I I, brass collar tinned into the copper tube formiug the air reservoir. The breech is screwed tight into this collar, having a leather waster between to ensure an air-tight joint. It is best to commence with the copper tube for reservoir, and thin sheet iron case covering the lock and barrel, as then all the other parts can be better fitted. Be sure the butt end is strongly brazed up, as it has to stand the additional force caused by the driving in of the valve.—T. A. ^

[4611.] — POLISHING VULCANITE. — There arc various methods employed to polish ebonite or vulcanite; the mathematical instrument makers treat it as brass—that is, for flat work they first use water of ayr stone, and then rotten stone and oil. Turned work is polished in the lathe with rotten-stone and oil, taking care always not to use too high a speed, so as to heat the work. Some nee lampblack and oil to finish with where a very high polish is wanted, and others, again, the bare palm of the hand, as in getting up silver platt-. Chain and ornament makers use circular buffs for then flat work, made of sea-horse leather, and for work of irregular forms buffs of calico. A number of pieces, lain, m diameter, are screwed together between flanges, like ■ circular-saw spindle, and used with rotten-stone, toxine care always not to heat the work; brushes are notât all suitable for it.—R. N.

[4612.]— PORTABLE MILL,—In reply to "Deri Errac," I have a model of a portable windmill or engine for pumping with any description of pumps, or the same might be used for any other pnrjrese, such as sawing, ploughing, grinding of corn, cutting chaff, or for any purpose where motive power is necessary.—John James.

[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 were formerly much iu use, but they have long since been superceded by steam power, as more economical and efficient. Gwynne'e centrifugal pumps are much used now, but they frequently blow, and require filling up with water for a fresh start.—Henry W. Reveley.

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

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A, zinc pan; B, honey, or sugar and water; C, floating board, perforated with numerous holes; D, outrance lor bees; E, top of hive; F, super or working hive. There is a piece of wood, which fits into it and floats on the sugar and water, perforated with numerous small holes through which the bees insert their proboscis, and get nutrimeut without getting their feet, legs, or wings sticky. The feeder is placed on the top of the hi ve,and the bees 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 any youth with a little ingenuity can construct for him soff, the little bees will produce more honey» and afford a constant and highly interesting study, for any time the bees could be 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 Hupers, is a very good one, and gives very little trouble to tho bee-master, and a strong healthy swarm will work three supers during tho honey season. Should my brother readers require any further information on beos and beekeeping I shall be glad to aid them in every way I can if they will ask through your columns.— Frank.

[4618.1—MANAGEMENT OF BEES.—Feeding-botUee for bees are ou tho 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 ayrup, have a piece of canvas and tie on the mouth as if you were tying down pro serves, 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, boles about the size of the head of я pin. Carefully tnrn the bottle of syrup upside down on this zinc. No more syrup will leave the bottle than what the bees will readily take up. See J. W. Pogden's pamphlet ou bees. To muko syrup I buy West India sugar, 4d. per lb., to every pound I add half a pint of water, boil for a few minute§, 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 lain, square, 9in. deep, commenced feeding, each night giving a bottle of syrup, about a pound and n half, and on the 37th of July tho 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 beos can get to it, ur you will have much .fighting and so loose your stock.—J. Lkk.

[4621.]-CHLORIDE OF GOLD may be made by dlssolviug tho metal in one part nitric acid by mixing two parts hydrochloric acid.—New Subscriber.

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

aold in a beaker or bottle and cuts the gold into small pieces will dissolve sooner. The deep yellow solution thus obtained yields by evaporation.yellow crystals of the doable chloride of gold and hydrogen soluble in water, alcohol, and ether. N.B. Place the dish containing solution of chloride of gold over the mouth of a pan contalninghot water, so as to evaporate the acid off.—Омхол [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 Hydrochloric acid. After standing a day or so, pour the water off, and get a clay crucible and mix the white precipitate (from solution) with charcoal and carbonate tf potash, aud place the crucible In a well-urged fire. x"ou will obtain a pellet of silver, which must be dissolved in nitric acid and solution crystallized in a water bath.—Omega.

[4024.1 —" YOUNG JOBBER."— The selection of a pendulum spring for a watch Is regulated according to circumstances, namely—a verge watch requires ono kind, u lever watch another kiud, the duplex different again, and the horizontal again differing from the rest. Presuming that he requires a pendulum-spring for the lever watoh, proceed as follows :—Select, or make, a pendulum spring to suit the size required, that Is, that the spring is such diameter that tho outer coil lies nicely between the curb-pins and free of the stud wheu* the eye of the spring is exactly central with the potence hole. Lot the spring contain about twelve to fourteeu turns there is no recognized rule,to determino the length of wire or number of turns chosen by springers. All they have to avoid, concerning this part of the matter, is that the turns are not too close to each other, nor too open. A good kind of spring will have its turne the distance apart of four times tho thickness of the wire of which it is made; the length of which will very much depend upon the size of the watch. In all probability the uverage length may be uin. to öln. Next find by counting the train of wheels—or by the old spring— how many vibrations per minute—or half minute—the balance must perform, theu eecuro the spring to the pendulum collet, attach it to the balance, hold the outer end of spring firmly by the tweezers, 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 continue for 90 or 100 seconds, during which time count how many vibrations the balance performs in the time required, say half a minute. Thus the springer is guided in the selection of a pendulum spring.—Seconds Practical WatchMaker.

[4625.]—FLUORINE.—This element must cortainly 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 lound in the teeth, more especially in the enamel, as well as In bones, particularly fodsil ones. It also exists in minute quantity in most animal and vegetable producís, in water, both salt and fresh, and in most rocks. There is, consequently, no difficulty in seeing how a supply of this clement Is sustained in the human body.—Trinitbophenic.

[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. Revele v.

[4627.]—DISCOLORATION OF LEATHER Is caused by the Irou press. All iron liquors or sulphato of iron will blacken leather. The proper way to make impressions is to get your impression made in white zinc metal, Jin. tnick. which should fit in a groove, made to receive it Fig. 1, In tho top part of the press, and be

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fore using it ehould be taken out and made warm, and then slid back into the groove again. Two pieces of flat white metal, cut at an angle and screwed to tho top part of the prees,|Fig. 2, would make the giones.— S. Scholefikld.

[4628.]—INTENSITY COIL.—Inanswerto" W. J. P.," I have made a coll 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 Darnell's battery, the shock is so strong that none of my friends dare 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. 1 have to stato that my battery is simply tbe Leclanchê, but without the accumulation.—W. H. St Une.

[4632.]—WEIGHT OF BALL.—Ralph Williams in this query makes it appear that my former answer is characterized by two errors. But I am pleased to say that I am not accountable for either of the (apparent; errors. I think that " R. W." himself is accountable for the first one, and the printer for the other. In the first place "H. W."potníi out that he thinks I have missed u point (I presume he means a decimal point). If so I beg to point out to htm that the said point will be found behind the figure 7 In my former answer, and not before it, as he places It, which makes all the difference—78Í4 beiug made to stand as '78.И. In the second placo the printer has misplaced a decimal point in connoctiou with the weight of wire, '5, or half a pound, being made to appear as Mb. I thought "R. W." would discover the error wheu he knew that the weight of tho wire was holf-apound. He will see that dividing by five and dividing by point live, give 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 irou is as follows: Multiply the equare of diameter by 2618, which Is tho weight In lbs. of a liueal foot of round iron, lin. diameter. In working out the weight of a foot of Jin. round wire tor my former answer, I found that it involved several places of decimals, itherefore took tho weight of a yard, which, coming вэ near to half a pound, made the process very simple. On referring to Ponn I find that he gives the weight of 3ft. of ¿in. round iron as '49; Sx>on gives '51. I take the mean and say '5, which is sufficiently approximate for all practical purposes. Of course I had to multiply the 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 hair», as I inferred from *' R. W.'s" first quory that he only wunted a rulo whereby ho could obtain the woight of round iron in the shape of round ball* aud round wiro, so I gave the weights in round numbers. I may now inform "R. W." that the '146 made use of to obtain tho weight of a wrought fron ball is the weight of a wrought iron ball liu. diameter. So that the cube of any sized round boll 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. But I do so with pleasure, hoping thereby to satisfy ■' R. W." Weight of ball 7in. diameter. 7» x -146 = 60-078. Weight of a yard of ¿in. round wire '262 * 7*864 = -490,875 For simplicity I take the weight as '5. Therefore



If " U.W." will invest 2s. in a little book published by Charles Fox, Paternoster row, viz., "1 Vim'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 find his weight too heavy for a cubic foot of cast iron? Most authors give It as 4501b. This will account for the Sib. difference between my weight aud his of a 7ln. baU.—Feebum.

[4684.1 — ELECTRIC I CLOCK. — TO " ELECTROMAGNET."—I may add that the clock is equally unoriginal, being a Swiss patent, exhibited in the last Paris Exhibition. I heard of it from my friend Dr. Grabham, of Earluwood, and procured one through his instrumentality. The English patent has been bought by Mosely, of Covent Garden. Tho 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.

[4685.]—CAKE COLOURS.—Procure a small slab and muller 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 aa possible, and dry with a very gentle heat. Old crumbling cakecolours, may be powdered very finely in a biscuit-ware mortar, and sifted through fine muslin, and ground up as above, omitting the gum water In the medium. If the powders are rubbed up with honey (degpumated) to the consistence of thick cream, they answer admirably as moût colours.—Sable.

[4640.]—SOU ГН KENSINGTON EXAMINATION Е'лí'l'Aíá. -Il " J. В. H." sends direct to South Kensington for the examination papers, they will be sent to him by secretary. Science and Art Department. Ho will have to pay tor them, od I think.—C. H. W. B.

[4648.1—TWO COINS.—The upper one is a PAXS peuuy of William I., possibly one of tho 12,000 or so lound on the property of a Mr. Dunn, of Beaworth, in Hampshire, in the year 1888. The obverse is PILLELH HEX (William King), and on the reverse is "OOMUND ON SUDE," Osmund being the money ег в name, and 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 tho Conqueror (v. Ruding). The lower eoin is a sixpence of Philip and Mary, date 1554. Value depends on condition.— T. W. Boobd.

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

[4652.]—TONING BATH,—I have used the foUowing for the last four or five years, and know of none superior for rich purple tones :—80grs. acetate of soda, lOox. water, 5grs. curb, of soda. This to be mixed some hours before wanted, and chloride of gold sufficient to tone the prints in haud added just before required for use. The bath works quickly hot and slowly when cold. I always prefer it hoi, and tho solution may be used over and over again, ad libitum. 1 may also add that for the last threo or four years I have always usod nitrate of potash in my sensitising bath in the proportion of 2 of silver to 1 of potash, and obtain richer tones and more glossy prints by so doing:—2oz. nitrate of silver, loa. nitrate of potash, 20os. water, neutralised by a little carb. of soda. I never have any " old" bath, 1 use it up until there is not sufficient to float my paper, and then 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 enable 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 ceutre at every 12o'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 the true meridian as to touch the northern tropic about li minutes (of an honr) west, and tho southern about Ц minutes east thereof. This leaning slowly increases, and will for mauy centuries; out the inequality of the two loops is decreasing, having been at its maximum six centuries ago, when the 8 was last upright. Tho leaniug is alternately to the right and left, for about 0,000 years each; but each loop Is alternately largest fur twice that period; and the southern has been largest ever since Adam's time, wheu they were last equal. The widest bulge of that loop is now somewhere about 15: of S. declination, and that of the smaller loop, 20' N. The crossing of the curve on itself is some i minute west of tie meridian, and about 10° N. • and its four crossings of the meridian are at some 'Jemand 10J N., at a point very near the northern tropic, and at one still nearer the southern. I expressly renounced the showing of truo clock time for a few days of midsummer and midwinter, namely, when the sun*s declination exceeds the last-named two points. I shonld rtdd 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. 2. Optical.—The solar shadow of every object is bordered by a penumbra, whoee 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 tho 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 is within, or less than, the theoretic shadow by half the sun's diameter at the time.—E. L. G. [4654.]— OCCULTATION OF8ATDRN— "Hesperus" will find no difficulty in interpreting the Nautical Almanac Bccount of this phenomenon if 'he' will refer to page 164, where he will find that tho horizontal parallax of the moon on September 80th is about 59-. This is the maximum amount by which the moon's apparent place in the heavens may be shifted from her plaee as supposed to be viewed from the earth's centre. Further, her semi-diameter on September 80th is more than 16', so that even though Saturn were 75' {i.e. 59' + 16) from the moon, supposing both to be viewed from the earth's centre, he would be occulted as seeu from лоте parts of the earth's surface. He is actually about 564* from the moon, southwards, at the time of conduction; so that, as seen from stations having more than a certain northerly latitude, he will be occulted.— li. A. Pbociob.

[4654-1— OCCULTATION OF SATURN.—Without examining the Almanac, it seems pretty plain that "Hesperns " must have overlooked the vwon я parallax. The elements he quotes, are doubtless given for the earth's centre, not Greenwich; and apply to the place where the bodies will be vertical. The Almanac does not predict au occultation there, but at Greenwich, which is quite possible while their geocentric distance is as great as be 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." —I protect my connections from corrosion with a small plate of platinum foil under the copper. I understand, 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 preesure per square inch on the bottom is the вате 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 tho following manner :—Take a plane tube A, and to tho bottom fit a water-tight valve, V. This may be preescd up by means of a lever, a b, as Bhown 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 oí 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 Rame arca ав that of À, 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 coure«. It is the most elementary fact in hydrostatics. —Ш. LG.

[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 6'29 lbs. —thomas J. O'connor.

[4666.]—PROBLEM.—a. Call the regular length of journey x minutes. The train proceeded regularly (W) minutes, then stopped for 30, and had to do the remainder, which would regularly have taken x — 60, at

three-quarter speed which occupied — (x — 60)—The whole took, we are told, x + 110 minutes. Hence

(A) 90 + 1(лг— 60) =

x + 110. Next, had the train

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ß. From |jf+80+|*-* + 80by merely omitting the 30 common to both sides $х + 3л-—jr + W, whence

1 x = GO, and x = 800, as before. So that the ß infonna


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

determine that the regular length of journey was five

hours.—E. L. G.

[46ва] —LATHE.—TO "TOMETER."—You ought to be a pretty good judge 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 about its price—pliw 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 а 4} lathe: nothing less than Б. 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 5in. You can add a leading screw at any time after all the rest is complete, and the bearings for screw may be 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 lese than that, and one of Smith, Beacock, Tannett, for a little more than half Whit worth's price.—J. K. P.

[4668.]—THE LATHE.—Perhaps "J. 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 suchas "Tonieter" describee. If he 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,—The kite would certainly not act as "W. J." describes, for suppose it to be suspended in the air as he proposes, and to be inclined at an angle, say of 451, which would be about the proper inclination; then the wind pressing on the iuclined 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 an these two forces would be equal, and supposing there be nothing to oppose or diminish either of them, the utmost the 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 45-. But seeing that the weight of the kite and its appendages 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 should have 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 np from the earth) provided it is held by a siring to prevent it going with the wind. A kite could no more work up into the wind withont 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 last number.—T. W. Boord.

[4676.]—NITRATE OF SILVER.—The sediment from "Paddy's," salted "slops" is chloride of êilver. His best plan is to collect the sediment in a large bottle, and when full, sell it to a chemist, together with all his old filter and draining passers, 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 published on the steam engine. •'Main and Brown on the Steam Engine " is also a very good work, but it treats principally on tho marine engine.—Thomas J. O'connor.

[4669.]—PEDOMETERS.—The motion of the body in walking causes the vibration of a short weighted arm or pendulum which acts upon a email toothed wheel, geared into another connected with the index.—Unit.

[4691.]— POWER OF ENGINE.—According to the rule to which "K. W." refers, the power of his engine at301b.pressure would be ¿ horse power,thue, 4 1

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

therefore three times the given pressure, orOOlb. per sq. in. would be necessary to enable the engine tu work up to 1 horwc power. With respect to the thickness of boiler plate, I must refer *'K. W." to some practical boiler maker, whose advice will be safer than mine, for 901b. is an unusually high pressure. If possible, it would be far better to use an engine with a Sin. cylinder, since then, the pressure need not be more than 4ulb , the expense of boiler being, of course, proportionately reduced,— Ver


[4698.]—BICHROMATE BATTERY.—The plates are usually about gin. or ¿in. between the faces. The resistance of tho solution is so small that I thiuk very little powder would be lost, and greater coustnncy be obtained, if they were lin. apart. The plan for connecting (given under the heads of "Carbons" and this battery in my papers) is the best possible—viz., electrotyping the top of the plate and soldering.—Sigma.

hours with the Telescope," can be gathered from ii* fact that the telescope was of the size mention* in "Turton"—that is, 4in. in aperture and 5ft. in !>.«al length. I do not recommend the stand a* атюЛу figured. The toothed wheel and quadrant ore toa expensive; and, again, the legged part of the «tend should be higher in proportion. The great toothed quadrant should be replaced by a semicircle wiihoui teeth; a cord carried aloug the circumference of the semicircle and making a turn round the axle driven by the endless screw in my figure, serving to give the continuous motion in altitude. In like manner a cord round the circle c, with a turn round the axle driven by the crown-wheel, would give the continuous motion, in azimuth. The figure is really a picture, with very «light modifications, of a telescope I used in 1У64-5, "now *t Marlborough School. The crown wheel I filed mysett from a part of the appurtenances of a window-blind. I also filed and set the endless screw, and a pretty piece of work I made of it, more by token. The lanlera wheel working in the crown-wheel was made by simply breaking a knitting needle into four equal piece«, and tying these (!) parallel to each other round the end of a rod. The instrument, when thus completed (!, «u a, singular combination of the expensive and the comm&aplace; but the knitting needle and the endless sere« arrangement worked well all the same; andtheeomfurt of having the two handles, which give the altitude ud azimuth motions, always in the same fixed and convenient position, was such as to make one forget the instrument was an alt-azimuth.—R. A. Proctor.

[4713.]—BEES.]—They will pase in and out through such a hole as you describe, provided you connect the entrance of their hive with it in such я manner as Ь prevent their escape into the room where the hive h kept. Move them at night, and in the morning ther will take the bearings of their new locality before con> mencing their labours, so asto be able to find their way back again. For feeding in winter, use a syrup made of white loaf-sugar, boiled down with water, about a pound to a pint.—T. W. Boord.

[4721.]—FOSSILS.—"H. U." ought most certainly to find some fossils in the locality between Cromer and Hunstanton. The Tertiary system is very fully developed in that neighbourhood, and amidst the Crag of the Pliocene group he mar chance to come upon the remains of small mammalia analogous to the mouse, also teeth and bones of placoid ft&hes, and corals, and shells of innumerable species ; marine plants are likewise to be found. The strata consist of marine and Iscnstrine deposits of shelly beds of sand, clay, and yellow Joani. arid flinty shingle, generally resting on the chalk sy.-tcm. "H. V." should wander into any gravel pit's or quArrfc«. &¿e., and closely scrutinize every rock иеяг which he comes; he should also provide himself with a hammer for the purpose of detaching specimen*. The chalk or Cretaceous system lies immf diately below the T «tiary and is rich in shells.—Arthur Undeuhill.

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[4725.] —SHORT-SIGHT.—Could any of your scientific readers give me a little advice under the following circumstances ? I am very' short frighted, so much so, that

I am unable to recognize a person ten yards distant, which is very inconvenient for my daily occupation. I am 21 years of age, and my sight has gradually got shorter binee 14. Is it prudent to wear spectacles (I have a great horror of them;, I have heard they strain the eyes and otherwise prove injurious.—Moses.

[4736. J -HOBOLOGICAL.—TO "NOBODY."—Thanks to " Nobody *' and others for their kind replies to хну queries, No. 4,12a. I never had the pleasure of reading: such a welcome communication before as that of

II Nobody's" on watch jewelling; and allow me to teU him I found it practical to the letter. Will that gentleman kindly inform me how to turn in a new verge, and also how to fit a balance wheel to a verge watch, naming tools to boused in the same, and oblige?—Compensated Balance.

[4727.]—TO "OMEGA."—I am very much pleased with the results given by "Omega" in Ыз pfiper on Slater's iron cclL Would ho kindly inform me where 1 can obtain nitrous acid at 4d. per lb., aad also nitrate of soda at 1 jd. lb.? I should very much like to know the results obtaiaed with his 86 evils.—A. J. Jailxam.

[4728.]—TO "SIGMA."—I am glad to hear that "Sigma" is going to compile his pr< tent papers into a book. Undoubtedly it will be about the beet w«rk on electricity. The iron that contain« d 65 per cent of carbon was a piece of common cast-iron gas-pii*e. i" would like " Sigma " to inform me h >« zinc can repbtce sodium in a solution of sodium chlori- e, as he а-*лг£$ it does; whüc in one of his former paper» he say* that zinc cannot replace sodium in a solutioaû/ sodium chloride, and I think so too.—A. J. Jarmas.

[4729.]—TO MR. ÍPROCTOR.—Mr. Proctor says a Arietis is visible in a Sin. Will he say what i* the angular distance and magnitude of the componouts? Dues Mr. Wrav .use a cement, liquid or solid, *s * concave lens in his glasses?—Ао,иж Solis.

[4730.]—NAIL MAKING MACHINE.—Can any correspondent inform me what would be the cost of amachino to make cut nails, and how many different size a one сад make, and also what power Is required to work one?— Nail Maker.

[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 very »mall quantity of »alt is sufficient; too ranch undoes it all. "In a Fix " ha»l better put all his future washings into another rang aud try to precipitate the silver by adding a little of the over-halted washings to it instead of salt, and so gradually use it up. Unit.

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

[4781.]—TO " SIGMA".—I shall esteem it a very у favour if "Sigma " will Inform me whether soaking a portion of a carbon plate with paraffiue, to prevent absorption of liquid, as suggested by him dome time since, would not have an injurious effect upon its conductivity.— Docdalos.

[4782.]—GAS-TAR,—Would " Sigma," or any reader

kindly inform me how gas tar is prepared, so thai it* alcoholic solution would forman emulsion with water. — Domino.

[4733.]—BRONCHITIS.—Can any of your readers inform me of a cure for bronchitis? I am much troubled with it, especially when I walk a distance in a harry, the tubes get full of mucous, aad expectoration is tie only reliof; At times the mucous is streaked with blood. 1 bathe the throat und chest with cold water frequently, and have found it a great benefit, bnt the disease or trouble is never away, and is annoying.—Omega.

[•1734.] REMOVING WRINKLES FROM PRINTS.— Will a brother subscriber inform ше how I can remove wrinkles out oí a coloured print? The print is fastened to the back of the framo with gum or some other adhesive substance, but in places it is drawn from the back audrose up in wrinkles.—Winner.

[478>.] PEABL OYSTER-SHELLS.—Can any one tell ше where the above are to be purchased and the price 7 —thus. Fletcher.

14736.] BALANCE IN VERGE WATCHES. — Will any of our watchmaking brothers enlighten one desirous of gaining knowledgo as to the beet way of uprighting the balance in verge watches when tho cock and potence holes are worn and want refilling, or have been refilled, and left with balanco leaning on one side? What I want is the bost and easiest method o! setting oat the holes so that they shall be perfectly perpendicular, as I find frequently that watches which have been so repaired fail in this essential point—С нее к-Ache.

[4737) BLO WPLPE.—I wish for some information upon tho practical use of the blowpipe. I possess one lOin. inlougth'of brass, andean manage to braze email articles such as watch hands, &c., bnt when I attempt to solder now Joint or pendant on watch case with silver solder it results in a miserable failure. I use a common tallow caudle, or is place oí which I uae a small benzine lamp filled with beuzoline. Then I placo a little powdered borax on tho joint, or whatever it may be, with the silver solder on tho top, then placing the article in my left hand 1 direct the blowpipe and flame with my right hand upon the work» and blow till tho borax is melted and the silver abo, which has been laid on in a strip, which runs into a small round globule glittering and dancing beneath tho heat of the flame. This is all that I cau attain. The fault appears to be that I cannot obtain sufficient heat in tho article to be brazed to enable it to take the solder (but I may be wrong), although I may blow till my cheeks acho and my eyes start. Is the fault in the blowpipe, the caudle, or lamp, or want of oxygen in the breath, or where is it? I know that snoh work is done daily, and hope to receive instruction through your columns.—Cheek-Ache.

[4738.] GEOLOGICAL.—There Isa matter which has puzzled mo much, viz., the "cause " of the intervening strata, or the sandstone rocks, which ¡ - found between the different coal beds. In other words, if the vegetation of the coal bed periods has been caused by the heat of the su» and season«, what has been the "cause" of the sandstone periods ?—Veritas.

[4739.] —COLOURING SIZE.—As no correspondent has answered my query, 4317, page 480, can any one tell inj- what to put into the size to make it a very pale blue, as I find oy putting indigo into tho size it makes it a green?—John Buby.

[4740.]—CONTACT BREAKERS.—WD! "Sigma." or souio fellow reader, describe the contact breaker of the large coil at the Polytechnic (or any other) that counteracts the destructive action of the spark ?—R. N.

[4741.] — DISSOLVING INDIA-RUBBER. — Would some one Inform ше how to dissolve india-rubber, so that it will mix with oil and turpentine ?—Rubber.

[4742.]—STEREOTYPING IN A SMALL WAY.—I have had many attempts at stereotyping in n small way, both by the paper and plaster of Paris processes, but havo always partially failed. Having read, here and there, about eleotrotyping, I have thought of trying that process, anil now wish to know whether, by taking an impression in gntta-pcroha 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, i.s the ртсеяз'moro 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 -tin. of mu<n: stereo, which I have obtained by a new process, and d<i-ire to prove? I should feel greatly pleased if aoino of your numerous correspondents would answer mc.—Gwouob.

[4743.] — HEM-STITCHING MACHINE.-Can any reader givo me any information as to the construction of the hcm-stitehfng machine, or how I may get to вес the specification of the patent ?—Aquillus.

[4744.]—GUN-COTTON.—Will any kind reader of our paper inform me how the above is made? I have tried equal parts of nitric and sulphuric acid; poured over cotton wool, it turned a brownish solonr, and some became like jelly, and after a thorough washing failed to he explosive ?—Experimentalist.

[4745.]—STARCH.—What eubstanco can be usod wíili the above to give linen a fine gloss, such as you see on collars, Ac, in shops?—Tidy.

[4746.1—SCREW CUTTING. 1 should be very glad

if our kind correspondent " J. K. P." would give me ■ ■in- information on the screw-cutting lathe. I have a four-foot lathe with hack gear and elide rest, the bed flanged same as ordinary screw-cutting lathes, and aaddle to fit. What I want to know is what form uf nut he would advice mo to nee? Being only an amateur, I do not want a complicated affair. I have bad a screw cut for the lathe, but no nut for it. Tho pitch is $in. square thread. Would he advise me to have a split nut or solid nut with bovil wheels to work with handle at the front? I see that he has sent some useful information on the lathe, which encourages me to ask him to do me and my fellow readers a great favour. —Joseph Museley.

.!?7ÍH"~ÜLA9S BDBNINO.—I am afraid Mr. Ashton will think me vory deiue, but I venture to ask him for a diagram of his brick furnace, described at page 476, also for replies to the fallowing questions :—What is the medium used for painting on the colours? Is it necessary to submit the painted glass to the action of heat after laying in each sepáralo shade, с a, as in flesh tints, draperie-, Ac.? The painted glass Is directed to be placed between layers of quicklime,—will not the limp mingle with the colour during fusion, and injure tta evenness and transparency, what kind of fuel is most suitable? Will the red protoxide of copper yield a good tuhy colour, nnd u\ide oí manganese ft good amethyst?


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

[4749.]—CABBOLINE.—Would "C. D. C." be kind enough to state where I can obtain carboline, and at what price per gallon ?—A. J. JArmAn.

[4750.]—SOFTENING AND PURIFYING WATER.— I should be glad if some correspondent could tell me where I could get a description of " Clark's putent for softening and purifying water," as mentioned by Dr. Franklund in his report to the Registrar-General for the month of July, and referred to in your number for August 19th, p. 132.—J. С

[4751.]—TAPS AND DIES.—In the Enolish MeChanic for August 5, W. Reed auks (4434) "if he can make left-handed taps and dies from a set of taps and dies for right-handed work," and on tho PJth "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 thia muaus alone .'—T. W. Boobd.

[4752.]—DIFFERENTIAL CALCULUS.—Will some one show me how to do this sum f It is in "Woolhouse's Differential Calculus," p. 87:— _1_

(trf + яе») , à » 8л*

Ja* + *3

the amount of steam contained then expand and do the same amount of work, as an engine without the

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F. P.

[4753.]—GERANIUM PROPAGATION.—Will a brother reader give me a few hints how to slip these plants, and whether or not I am to put anything tu the bottoms of the slips?—J. E. Clay.

[4754.]—DRESSING SKINS.—Will any reader kindly inform me how I can dress into mat > such skins as sheep, deor, and dog ?—Та We в.

[4753.] —CONICAL WINDING DRUMS.—Will some brother reader kindly give some particulars respecting the construction and working of conical or spiral drums as applied at collieries for drawing coals, and state what conditions are to be observed in order to ensure their safe working ?—W. M.

[4756.] —CONSTRUCTING MAGIC-LANTERNS.—Can any of your numerous readers inform me how to construct a magic läutern; where the lenses may be procured, the prices of such, or how to grind them; and material required for such purposes ?—A. Storment.

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


[4758 ]—FRESHWATER FISH AND FISHING.— Being an ardent follower of " Old Izaak" and "the gentU craft," I always road with interest "A. T.'a " replies to questions. Can he inform me of any placee near London whore good fishing can bo had on payment of u small fee; or where permission can be obtained on writing for tho same? The great drawback we workers in town havo is the difficulty of finding spots near at hand where, in our few hours stolen from toil, we can seek recreation at once harmless, healthy, and amusing. —Pimcatob.

[4759].—POLISHING WALKING-STICKS, Etc.—Will any of our numerous contributors kindly tell an amateur tho best polish to use for walking-sticks, umbrella-sticks, До r—Whitethorn.

[4760.]— EXPANSION OF STEAM.—1. In Spon's "Dictionary of Engineering" under this head, page 428 (article "Boiler"), it is stated that "the dual logarithm of a given number can be calculated without the use of tables in a few minutes." As my table of hyperbolic 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 ablo to employ H (?) for any ratio oí expanBion. 2. Not being up in logarithms, would auy kind brother reader give me a table of hyperbolic logarithms of numbers from ten upwards to twenty, and also explain how the h vperboliclogarithm of a uumber and fraction (or decimal fraction) of a number between units and fractions of units in table is determined. Example: Let the number be 4*70. The next lower number in table is 4*60 if1!, for which the hyperbolic logarithm 1-5040774 stands, and the next higher, 4'75 il;) for which the hyperbolic logarithm Г5581446. I want to know how I am to find the hyperbolic logarithm of No. 4*70. 3. What is the rule for Unding the end or ultimate pressure of steam (not the mean) for any given degree of expansion? Does the preesuro decrease exactly in proportion to the increase of volume ?—A. W. E.

[4761.]—SLIDING RULE.—I wish to know how the Bcalos, or rather the divisions, are laid down, that is, set out on tho sliding rule, for working proportions, areas, divisions, &c. Information will greatly oblige. —robert Bridoart.

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


"J. В h," bavin« examined the recipe ач described

by " Sergius," cannot understand the composition of bell metal, thinks It may «1 > very well for iron and brass, but is afraid to use it for Britannia metal. The latter being so soft, whilst bell metal so hard. "Sergius's" reply would oblige.—J. В h.

[4764.]— BRONZING COPPER URNS.—Cananyof yonr many readers inform me of a simple way of brouxing urns for hot water, chiefly used on the tea-table, value about £5 each, colour very dark copper colour.—J. В h.

[4765.]— PISTON AND PRESSURE.—A representee east iron cylinder fastened to the piston-road as shown, and working through tho bottom of the steam cylinder in the same manner as an ordinary horizontal engine. I will suppose the engine to be an expansive one. Now in my plan the piston, having its full surface exposed to the steam, must, when the port« nreopon, have the same pressure on it as though the cvlir;dcr A wero omitted. Bo far all li.j'it, but when it (the steam) is cut off, will

cylinder A ? * I think it will, because of the piston allowing its lull area to receive the pressure; bnt would like to know if theio are any rules to determine the force of my argument.—Окк.

[4766.]—STAUNCHING TIMBER JOINTS.—I would feel much obliged by any reader informing me as to the 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 use ?—Antares.

[4767.]—"MODEL PADDLE-STEAMER.—I am making a model steamer (paddle), about 7ft. long, and wish to tit air compartments to prevent immersion; will some kind reader inform me how to do it, and what to make them of?—Т.К.

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

[4769.] —CIVLL SERVICE EXAMINATIONS.—Can any reader givo mo information respecting /he alteration in the Civil Service? Why tho examination i* done away with, and what course of study it involves? I shall feci much obliged for any information on tho subject.— J. M. C.

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

[4771.]—FLUX FOR BRASS, GUN-METAL, ftc.—Wffl some kind reader inform me what flux is used for brass, gun-metal, &c, and how? In running tho metal into a mould I find it leaves a crust hanging from the crucible, and however smooth tho mould may bo it turns spongy, and not solid, therefore very often of no use. Tho flux, 1 think, clears it in a great moasuro.—Lilliputian.

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

[4773.]—CAUSE OF THE EARTH'S REVOLUTION. Can you give me any idea what causes our earth to revolve У I can understand it being set in motion, but 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 Moee.

[4774.]—THE ALLANTHUS.—Will some of yoRr correspondents kindly give me some particulars of the Ailanthus silkworm? I wish to breed a few. 1. When does the egg hatch? 2. How long before the larva becomes a chrysalis? 3. When docs a chrysalis hatch ?j 4. Where is tho plant to be procured upon which it feeds? 5. Where can I procure somo eggs? I have seen the names of other silkworms but do not know where to look for them, but shall bo glad to have particulars uf one or two of them also.—A Constant Readeb.

[4775.] —LUMPS ON HORSES.—Will any of yonr readers kindly inform what they consider tho best cure for small lumps on horses, commonly known аз "heat weals,* and what to apply when they break nnder the collar ?— A Grooh.

[4776.] —LATHE.—Yonr correspondent T. W. Boord, gives the numbers on the division plates of lathes by different makers. It would interest many to know the size and pitch of the screwe on tho respective mandrels, and whether tho same gauge is adapted for " ornamental lathes " as for those for general nse ; also the diameter of the dividing wheels and pulleys of each lathe. I presume the lathee referred to arc 5in. centre.—Amateur Turner.

[4777.]—LINK MOTION.—I am surpriaod to seo "R. W. В 's" question (4581), \fter the very clear and Intelligible papers by Mr. Baskerville on the subject. May I ay; Mr. Baskerville to explain a sentence in the last paragraph but one in his last letter about the stationary link as applied to the locomotive? He says it requires " a length altogether out of the quostlon in a screw engine or a locomotivo." To what extent the word properly applies I know not, but there are a large number of engines running on the London and NurtnWeetern, and London, Tilbury, and Southend Railways with this motion.—G. W. A.

[4778.1—DENTISTS' CEMENT.—Can some one inform me how the cement that dentists nso in fixing the teeth in the metal is made?—X. L.

[4779.]—HOLTZ'S ELECTRICAL MACHINE.—Will "Sigma," or any other correspondent give a description of Haltes electrical machine, or state in what work English or French, the same may be obtained? —A Revenue Officer.

[4780.]—TEMPERING STEEL NEEDLE WIRB.— Will any one inform a brother reader how to harden and temper fine steel needle wire in SO or 40iu. lengths? —an Old Subscriber.

[4731.]—SUSTAINING BATTERY.—Could "Sigma" or any other electrical reader give me a description of the L attcry used for working Tyer's railway block eignab;? It has been described to moas a box containing eighteen stoneware cell', and at the bottom of each cell there is something very bright like mercury, this is all the information I could f£ain on the subject. I am very anxious to learn what this battery is, and how long It will remain in action.—Cods.

[478a.]—TOMATO 8AUOE.—Can any reader give me a simple recipe for making the above sauce ?—Bon


[4783.]—CONVEYANCE OF WATER.—How much power can be utilized from a supply of water conveyed 150 yards in Hin. piping wiih a fall of 13ft.? What Is the best means of gi.uing that object«—sorablning the attainment of the greatest percontn^e oî power with sini

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