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bargain 12-ca*adle gas; according to Dr. Frank land they give 12*1, that is they have fulfilled their agreement, and it is travelling out of the question to say that under other conditions other cities have better gas. The real trnth, however, is that only on very rare occasions is the gas anything like this, and the aver age is probably over 13 candles, and in no single instance that ever I heard of has the gas eyer been, an stated, 9 candles, unless absurdly burnt.

Snch an assertion as that the gas now is worso than it was years ago is really too absurd. The only real basis for it is an apparent increase in the quantity of sulphur, while there is really a great decrease; but within the but few years the process of testing has been so greatly improved that what previously passed undiscovered is now detected, as the gas referees appointed in the interest of consumer* pointedly show, and thus as fast as the companies succeed in removing more impurity, so previously unascertained impurities are presented. The best answer isthatitpaya to purify, as the impurities, when collected, are valuable and saleable matters. Sigma.

ELECTRO-MAGNETISM A3 A MOTIVE POWER.

[313] Sib,—Many people have endeavoured to utilize electro-magnetism to work machinery, and it is easily accomplished in many ways, bnt it is extremely improbable that it ever will become a practical source of mechanical force, except for small work and special purposes. The only thing which would render this probable is the discovery of such a source of electricity as would be nearly costless, and tills is quite possible, as many chemical changes are carried out on a large scale for their final results in which the force they give out is thrown away. In fact I quite clearly foresee that the day will come when chemical works will concentrate themselves, and distribute the electrical force they now throw away, and send it out by conductors for use elesewhere, just as is now done with gas and water. But the ordinary conditions reverse this state of things: our batteries are worked for their electric force, and their chemical products thrown away, and under these conditions the cost is so great that it cannot compete with steam.

"Thinker" (p. 544) has correct views to some extent, but he has not yet carried that extent far enough. His idea that a coal fire is an electrical battery, is thus only a partial trnth, thongh a favourite notion some time ago, before the grand doctrines of the correlation of the force were established, and the modern clear ideas of the nature of force fully devoloped. Every chemical action and every mechanical motion is a translation of energy from one form to another; whether it is to take the form of heat or electricity, or mechancial motion, or be stored np quiescent to be again set free, is governed'by the conditions of each case. But let me beg "Thinker" to cast away all notions as to M electricities nniting" to canse heat, Ac., because these were the roundabout inventions of days when the nature of forces was little understood, and men were determined to have some definite embodiment of what they did not comprehend, instead of waiting for fuller knowledge.

The real point lies here : in burning ordinary fuel wc seldom utilize more than one-tenth of the force, that is, we waste nine-tenths in the process of conversion of latent force into motion. We can convert electrical force into motion with less loss, but the present known means of conversion of latent force into electricity are much more costly than those by which we can obtain heat; in fact, they are generally the results of several previous processes in which force has been rendered latent by chemical decompositions, as by reducing tb ores of zinc, a much more expensive proces than the exactly similar one of reducing what we may call the ore of carbon, i.e., carbonic acid, by heat from the sun and storing it as wood and coal. The economy of electro-magnetism as a motive force depends, therefore, upon the relative costs and proportional losses of these several processes.

Now we do not, as "Thinker" supposes, collect all the force of a battery in the two wires and utilize it; part is lost in the liquids which are heated, so also in the wires themselves, and in fact throughout the whole circuit. The point on which "Thinker," like most others, really fails is, however, I think, in overlooking the fact that an electro-magnet requires time to develop force; although the current generates magnetism in an infinitesimal period, the foil power is only reached gradually in a time dependent on the quality of the iron or its specific resistance to molecular changes; the purer and softer the iron the less time needed; therefore when numerous changes take place in the circuit, the magnetic force generated is small, the power developed by the battery is uRed up in producing molecular changes, passe*) into heat, and is lost, instead of into magnetic power and motion. Sigma,

SCIENTIFIC EDUCATION. [314] Sir,—Generally speaking he must be a bold man who would introduce innovations amid old established and well-known customs, but there are times when it is necessary to speak plainly, and this must be myexensefor troubling the readers of the Enolish Mechanic with a long dissertation upon education. The topic has lately and will be again in the minds of every one. Unfortnnately a great calamity has fallen upon the nations of tho earth, and the surprise and consternation created by a dreadful war erases every other subject for tho time being from the tablets of our memory. The Quakers are right; it is inhuman and barbarian to lead our fellow-men to the shambles for wholesale slanghter. Let our cry arise compelling the great ones to snbmit their differences to arbitration,

and let us determine to evade to the utmost being drawn into* ■M^ainary war, declared for no earthly rcatson except the ambition* designs of one or two nan. But I must not allow myself to be led into a dc•damat-ry essay npon war. Ttiiaiauot the time, not tttttaee, for such a subject. Thinum of every EnglishMiti'frihoiild be to se-dctha welfare ef his nativueauntry; nils in order to do this we mast know exactly what she has, and what is wanting. Vary tritely a contributor to Nature summed up tiii question: "Education and science," he says, "at the present moment are England's greatest needs.*' And he is quite right. Just for a moment then we will endeavour to inquire into the exact position of Knglond as regards these subjects. Edaeation may conveniently be divided into three kinds: a Primary, /S Secondary, and t Highest. Of then© the first has but just now been-dealt with by Parliament, and I am sure the Bill passed daring the last session, through the exertions of Mr. Farster will not lack the hearty good wishes of tho whole population for iU success. Time, and time alone, will provo its worth. The but of these three kinds will aeareely claim our attention at the present time; so it is Secondary education, the education of the w» chauical and middle classes, the stay and backbone of England, that attract* our notice. What eon be said for it? Little that is good. Certainly here and there, good schools under able conductors hare sprung up, but they are the exception not the role. The majority of these schoobt are under the direction of speculators, men incapable to doing the work required, caring nothi-t*** whether that work hu doao or net, no that they live comfortably and are never required to exert themselves. I am writing this from a town containing some tire seer*, of so-called middleclass schools, and of theso there are but about three deserving to be called schools. I could not describe the principle of the remainder, or the, ordinary, " school routine/' without giving seme clue to their whereabouts. Perhaps, however, it may open the eyes of parents to hear such facts a.-, the following: —A friend of mine was engaged by a lady to give lectures to the young ladies of her establishment. During a conversation which occurred, the lady principal said

"Could you not. Mr. M , teach Miss A, B,and C, $o

and-Mo ) It would be a good thing for them to go home and say, 'I am doing such and snch lessons at school.' It would be mentioned to friends, the prestige of the school would be raised, and an increase of pupils would be the ultimate result.'* Thus the nsefnl was to give

way to the worthless ; bnt happily Mr. M was not

compelled to remain in a situation in which he could not conscientiously perform his duties, so he did nothing of the kind, and left at tho end of the terra.

I constantly read in the cor re spen deuce columns of our Enolish Mechanic, that English houses cannot turn out certain work to equal that of Continental labourers. There mnst be a reason for tain, and may it not be assigned to the lack of scientific training v The eye has not been trained by the inspection of beautiful works of art—the hand has not been trained to draw cunningly devised and elaborate designs of machinery or architecture—the head has not been trained to adapt the natural laws which regulate the universe, and hence so much heartburning over ill-adapted inventions, inventions utterly worthless, but over which men have spent years of labour, and scores of pounds. Even now we are constantly be-dinned—ay, and by experienced workmen too—with the feasibility of " eternal motion." Friction, wear-and-tear, Ac., &c., can all be overcome. It was but last year that many pounds were spent upon a machine in this town for the above object; the originators knew they could do it, but they haven't, nor would they listen to advice. Again, but lately, auother idea concerning "perpetual motion," was mooted and worked out in the brains of two workmen, and they would, but for your hnmble servant's objection, have spent their all upon a worthless scheme. In every town it is so, and will be till scientific education has entered upon another phase of its history. Our schools, under the present system, are useless. How can a man teach science who is utterly ignorant of it himself? We have here a clue to our failures. The masters are incompetent, and the work is not done. Let us have some recognized diploma which every professional man ghall bo compelled to obtain before entering upon his scholastic career. A plan has lately been mooted which meets with approbation from men celebrated for their knowledgo of the subject. It is this—that we start de novo, gaining experience from previous failures. A society of principals, assistants, and all interested in the question must Imj formed, for individual exertion is of no avail. I will, again, take the liberty of quoting from a letter which appeared in the columns of a contemporary on August 4:—

"This society should have certain objects, and its members combined should use their utmost endeavours to assist in carrying out theso objects. A few of the aims would be as follows:—

I. The institution of normal colleges for the training of gentlemen who wish to enter the scholastic profession.

II. To recognise somo examination, diploma, &c, as sufficient gnarantee of the capabilities of gentlemen entering the profession, and insist that such gentlemen shall have this diploma. The evils arising from the incapability of so many of our masters cannot bo overestimated.

8. The necessity of Government or other central supervision and examination of every school. At the present moment the standard of a school is calculated by nothing. ... It is impossible to decide upon the general tone of a school by the examination of a few of the best boys. (In many schools a few of the best boys are regularly sent to the Oxford or Cambridge middle-class, and other similar examinations. The

public do not know the . sent).

4. The institution of a dab-hon-* appointments could be cnade, fritim .and soma means atttvehed t* it bt «. . agents could be avoided, t i the agents prey upon the • assistant pays all, and the all at j whilst the rich pruu-ipaJ u*-ets both benefited to the siime ei bear the^*# if it be found I

5. Periodical meetings, Saeh, then, is a rough

by the editor of the Q*-*r who has already £*s*PBM eeoiative gentlemen for A pr to be held immediately, wt&ei derided upon. Till now a. plineduen, mingled wiih eisWi leaders nfn*rh of uxulettKiend been frnitlwulj contendii of ignorance. Is flu- to wide and exposed, the -ampftrr-i i before the combined efforts of ther do not for a moment believe that ffairfj \ noble men will be fruitless, but may, i prove conquerors. Men, be npanrtetr-^t tight; the task is difficult; hut. witi I.' wheel, who dare stand in the road?

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BATTERIES.

[31G] Sia,—I am inclined to atgreow-t* marks of "M.R.C.S. a Saw Sab. " iZoO* is""Sigma" might have been a little m*rc en* explanation of the sulphate of lead and Cja** batteries. I have had a sii-eell batter) in -v*-* for fourteen months for dome&tic purposes c- * the whole of that time I have had no trouble *they only requiring water to compensate !& -n tion, and I can assure "MJi.C.S."" tha.. speaking, they are as powerful now u *^* charged. They are made as follows :—Cwt a —"I glazed inside, in which tit a cylinder of arc as>thick; next get a porous cell that will fit easi; r cylinders; now get some thin sheet-eopp-r aa' four copper cups about 2in. diameter and *i- J one above the other and about liin. apart copper rod iin diameter, this will be the c*=r ■ Now mix sulphate of lead with water to the -**-l of clay, and fill the copper cups with it, p-' in the porous cell and nU with water, chart cell with sea-salt and water and it is ready: examined mine the other day and found. bW wear in the zinc, in the copper the loss %f ceptible. I am now trying the mangimeae bal* of which I have had in use seven months,.* I am very much pleased with their action. 1*' a sketch to scale (if worth inserting) of tho U*

Joh>

NORFOLK GEOLOGY.—At the reoent m**ti London Geological Society the Havfc Jons read a paper "On the Relative Pojtfij.in Forest Bed of the ChUlesfurd Clay in Xorl-. Suffolk, and on the real Position of tfcb« Bed," in which he stated that both at Eas:t:.u and at Kessingland tho Forest Bed is to' forming part of the beach or of the font of tho c underlying the Chillesford clay. He consider the soil of the Forest Bed had been dap* ic-at < > estuary, and that, after its elevation, trees of «ti stools are now visible along the coast, grew ujpori tho true forest bed was formed. After tho eubuai of this, first freshwater, then fluvio-marine, and marine deposits were formed upon it; and Dm proposed to give the whole of these depoait* th of the " Forest Bed Series." The author sjuoetd the Forest Bed itself is represented inland by tb bed which lies immediately upon the chalk aiid t it and tho fluvio-marino and marine crags, bi^ being that the surface of the chalk, after enppo forest bed fauns, was gradually covered np bv sue crag deposits.

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he front taken off; Fig. 3 is a plan of the same at the ine ■■: ;I; i .* 1» i ■■ the diaphragm, the face is of stout tin, .ad the sides of very supple leather; B is u bracket, unnecttd to same at the joints or hinges, H H; G is he guide rod, carrying tho bracket B; L, the lever ixed at top of guide rod; S T, the stuffing-box, to preent the gas getting into the top of meter; T, tangent jr regulating meter; W,toothed wheel, fixed on spindle onnected with index; S, spiral screw to turn W; C', rank to work valves; V, valves. I have only shown •no lever and valvo in Fig. 1, to prevent confusion, C s a little brass catch, with a weight at one end to keep t upright, which catches the tangont rod each revolution, and preveuts the meter being worked backwards • y dishonest persons. The gas goes in at the pipe larked "inlet, and through the one shown by the dotted hie from A, and enters the valve box at the hole shown n Fig. 3. It then passes through tho valves into the iuphragms or measuring chambers, back again hrough the valves, and along the other pipe, shown by totted line to B. The inlet and outlet pipes are carried town the sides of the meter below the dotted line, but hey only act as siphons to catch the condensation. Tho :iapbragms move backwards and forwards like two pair i bellows, and as tho outside is used as well as the inide, it thus makes four measuring chambers, which ro filled and employed alternately by the action of the dives. The distance over which the diaphragms travel t each revolution is regulated by the tangent T being loved nearer to or farther from the centre spindle to hich it is fixed. The valves have three holes or ports; \0 middle one, marked No. 2, is always covered by the p of the valve, which is hollow and just large enough 'cover two holes at once, which are then connected. he bole that is uncovered is open to the gas coming om the inlet, and No. 2 is always open to the outlet ipe. Nos. 1 and 3 are connected with the inside and utsido chambers, which are thus alternately connected fith inlet and outlet. There is a cover to the valve box, ^io that trie gas does not get into the top of the meter, md the crank spindle works in a stuffing-box, the same is the guidorods. The two marks at top of meter are _, ;he Government stamps. They are put there because '-he meter cannot be altered to register faster or slower, ixcept by tuking tho top offand moving the tangent.—

FoHX H. RtfMSKY.

[4159.]—PHOTOGRAPHY.—I would advise "Young Photo" to give " Newman's Diamond Negative Varnish" i trial, and I don't think he will give it up. It requires re/y little heat, dries a clear surface, and never gets *:acky. I have used it for sometime, therefore speak from* experience.—John Terhas.

[4200.]—PRECIPITATING COCHINEAL.—The following is taken from W. A. Miller's "Elements of Chemistry," Vol. III.:—"After troating the powdered insects with ether to remove the fat, the insoluble portion Is digested with water, and precipitated as a purple lead bike by plumbic acetate. This must be well washed, decomposed by ■ulpuuretted hydrogen, and the filtered solution evaporated to dryness in vacuo over sulphuric acid. The resulting body is of a purple brown colour, very friable, and soluble in alcohol or water. By adding alum

and ammonia it is precipitated as a crimson powder; the alkaline earths give purple precipitates." Green precipitate is obtained by mixing solution* of cuprio sulphate (ornitrate) and sodio carbonate. I have often obtained this precipitate, but not recently, and I do not remember whether it is dark or light.—Oxohxknhis.

14234,]— TREATMENT OF A CHRYSALIS.—Pup» of such insects as require to be kept damp should be kept in A common flower-pot filled with light earth. In this they should be buried about Jin., and outop of the earth there should be kept a rag moistened about once a week, just sufficient to prevent the earth becoming dry. Othor kinds do not require auy particular treatment. —A. S. C.

[4242.]—INCRUSTATION IN BOILERS, ,eto.—Tho following description of an invention for the prevention of incrustation iu boilers, is extracted from the Student and Intellectual Observer, No. XIII. (February, 1889> .— "Among the many inventions for effecting this object, one by Mr. C. Weight ma a Harrison, of Clapham Junction, is simple, aud seems to be founded on a scientific principle. He suspends in the boiler a plate of metal— of course immersed in the water—which is connected with the metal of the boiler. The boiler farms one electrode, the suspended plate the other. The size of the metal plate is so proportioned to that of the boiler, that the electro-chemical action upon its Interior surface shall be what ho terms nascent, or nearly so; and he states that he finds it merely necessary, under ordinary circumstances, to impart a polarity to the shell of the boiler, in order to prevent the adhesion of the precipitated matters. Sometimes he varies the method of carrying out his invention by menus of an additional electrical source, so arrauged as to transmit alternately positive and negative currents to the shell of the boiler, and to tho suspended plate. This arrangement is found greatly to facilitate the production of steam." It is possible, however, that as " A New Subscriber " dates from Brussels he would meet with many difficulties—leaving cost entirely out of the question—the extent whereof alone would prevent the adoption by him of the above invention, although fully convinced of its utility. To obviate this (assumed) difficulty, to a certain extent, I may mention that sal-ammoniac is capable of re-acting chemically, to dissolve, in part, the incrustation; and carbonate of potash, to decompose without completely dissolving it, leaving, it must be admitted, at least car* Inmate of lime insoluble, and capable, under certain circumstances, of still forming a scale.—S . . . . B,

[4270.]—CHEMICAL.—Tho following is taken from Fowues's "Elementary Chemistry" :—" Magnesium may be prepared by reducing with metallic sodium the double chloride of magnesium and sodium, which is formed by dissolving caustic magnesia in hydrochloric acid, and adding an equivalent quantity of common salt, evaporating to dryness, and fusing tho residue. This product, heated with sodium in a wrought-irou crucible, yields magnesium, which may bo freed from impurities by distillation. Metallic sodium may be prepared in the laboratory by distilling in an iron retort 717 part3 of dry sodic carbonate, 175 paits of dry charcoal, 108 parts of dry chalk. These materials must first be well pounded together. Potassium is prepared in the same way from its carbonate, which is prepared by passing carbonic acid through a solution of caustic potash."—

OXOKIEXSIS.

[4274.]— CUPELLING.—The bestandmost practicable method of cupelling is to make a thick crucible of calcined bone-dust, using stale beer to make it into a paste and shape it, then bake, and when thoroughly dry, place in a muffle furnace and then put in the metal. The bone dust will absorb all but tho gold and silver, which will remain in the cupel in the form of bead. The gold can then be separated from the silver by putting tho bead into a parting glass nearly filled with aquafortis, using a sand bath with heat, the gold remaining at the bottom perfectly pure. Pour off the solution (nitrate of silver) and add common salt to precipitate it.—M.R.C.S. (A Now Subscriber).

[4275.]—TESTING GOLD.—The only method of testing gold otherwise than applying pure nitric acid to the surface (as far as my knowledge of the subject goes) consists in "cupelling" (see answer to No. 4274). The metal should bo weighed during each stage of the process.—M.R.C.S. (A New Subscriber).

[4881.] —METHYLATED.SPIRIT.— It is no doubt true, as '* A Revenue Officer" says, that persons have been fined for disguising methylated spirit and passing it off as a drinkable alcohol without the naphtha, but notwithstanding this, methylated spirit may undoubtedly be drunk as such by any person who finds the flavour to his liking. As a rulo all the tinctures now sold in chemists' shops, are prepared with the methylated spirit, and many of such tinctures are for internal application. If "Shellac" desiros, I will give him the address of a chemical factory where tinctures of all kinds are made from methylated spirit.—T. L. H.

[4376.]—COD-LIVER OIL, to prevent nausea, should be taken floated on a little cold water, in which had previously been mixed ten to twelvo drops of diluted phosphoric acid, which has a tonic effect, and makes tho oil agree better with the stomach. Tho chest should likewise be well rubbed night and morning with equal parts of cod-liver oil and whisky, to be well shaken before applied. The whisky causes the oil to strike into the luutf. To prevent the oil staining the linen a pioee of oil silk with a bit of flannel noxt the skin will be required. My wife has tried the above for the hist three mouths, aud urn thankful to say has derived much benefit.— H. K. N.

[4380.]—COLZA OIL is a general commercial name employed iu France, Belgium, Ac, for the oil manufactured by exprossionfrom the seeds of different species of Bra&sica, and has there the same signification as " rape oil'' iu England. "Colza," koolzaad, moans cole or cabbage seed. "Colza" is the French name for " rape seed," says Mr. P. L. Simmonds, in his " Dictionary of Trade Products."—BernAbdik.

[4450.]—BATTERIES.—As "M.R.C.S." desires some one else to answer his queries, I will do so, though, I think, if he carefully reads our over-obliging friend "Sigma's" answer.and substitutes the word "dear " for "clear," it will be much the same in substance. To query first, no. Second, the bichromate is the strongest, but the Sniee keeps iu action longest; tho length of time

of course depends on the work it has to do. Third, Smee's. Fourth, answered by tho secoud. Lastly, yea.— R. M.

[4481.]—A DIFFICULTY.—In answer to "T. A. Burge" (p. 502), I may say that tho standard barometer is usually provided with, an ivory or metal point, us mentioned by Tomlinson, to which tho surface of the mercury iu the chamber is raised or lowered by means of the screw before reading. In some, however, the scale and point are moved to tho mercury, instead of the mercury to the point. This adjustment, far from being clumsy, is extremely flno and accurate.—A. M. W.

[4490.]—WELDING CAST-STEEL.—Take loe. smelts blue, ioz. rock salt, 2oz. borrocks, pounded together and fused in a ladle over the fire, and when cool reduce to

Eowder; heat the steel to what Hiniths call a greasy eat; use the powder the same as sand. The weld will be much stronger if veed together iustead of common scarfed.—A Blacksmith.

[4517.]—STAINING GUT FISHING LINES.—Gut may be stained a pale brown and favourite colour by steeping it in a strong decoction of warm tea. A blue colour may be given by Bteeping in a weak logwood decoction for about five minutes, and rinsing afterwards in alum-water.-—ViviB Speaandum.

[4518.]— MYROBALANS aro dried fruits of different sorts of TerntinaliOy myrobalau order or Com,bretaec#t imported from India for the use of dyers aud tanners. —Bernardin.

[4518.] — MYROBALANS OR HYROBALONS.— Under that name, are imported from India the dried fruit (a drupe) of several species of Tenniitalia, chiefly T. Bellerica and T. Chebula, which are used by tanners and in calico-printing for producing a black dye.— Samuel.

[4520.]—PERCH FISHING.—Tho best time for perch fishing is just coming on, and good sport should be had from now right up to Christmas. There are no fish (that I could ever find) nearer London than, say, Hampton. Fish for them in deep holes, dark corners, under steep banks and near large beds of weeds; as a rule, big fish are never found in shallow water. Use a rod with a stout top and running tackle, good red worms or (forlarge fish) minnows; hook the minnows through the back under the back fin, in preference to the lip, as the perch seizes tho bait crosswaya ; by tbia method, the hook is at once in his mouth, and yon can strike immediately. The" paternoster" is a very killing way to fish for perch, but I would not recomtneud an amateur to try it as it requires some considerable practice to get into the way of using it.—Terminal.

[4520.]—PERCH FISHING.—The season for perch fishing is from February till October, during which long period they bite with various degrees of readiness, at all hours of the day; a little ruflle on the water assists the angler somewhat. For small perch a "general rod" will suffice; a common lino with good-sized gut, and a No. 4 or 5 hook baited with lob worm, grub, or caterpillar: a paternoster lino, armed with various baits, is useful for an unknown locality; and perch swim and feed at all depths. For lar^e perch, a strong rod line and swivel trace, armed with minnow or gudgeon, is usually the most killing bait; spinning by tail aud gorge hook is also successful, the hitter especially in water where there are many weeds. Most canals or slowrunning streams afford perch fishing.—Vivis Spe

RAHDUU.

[4521.]—EXTRACTING HONEY FROM THE COMB. —Cut the combs in a horizontal direction into small

Eiecoe and place them in a sieve over an earthen jar. 'raining may take two or throe days, but the greatest portion and the best quality will be drained off in a few hours. When all that can be got by draining is obtained, the combs may be pressed by hand, but tho honey so obtained will be inferior both in quality and colour, as a portion of bee-bread would be pressed through the sieve. If an "Amateur Bee-keeper" wishes to get honey of the finest quality, he must strain the combe from tho outside of the hives by themselves, keeping the first drainings separate, as the combs from the centre of the hives are usually darker coloured, and the honey not so good. They should be put to drain in a warm place near a fire. The remaining combs can be made into wax, which I should be glad to explain, if an "Amateur Bee-keeper" desires; but ho will find a great deal of very useful information on all points relating to bee-keeping in No. 3 of "Manuals for the Many,"—S. W.

[4524.]—STEAM JOINT.—I think if "Schemer" had a joint made like the one I send a sketch of, he would

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find it answer his purpose exactly, although I never tried it myself. 1 is a ball-joint, 2 a common stuffing box and gland, 3 pipe from tho engine, and 4 pipe from the boiler.—J. S. S.

[4531.]—SODA CRYSTALS.—According to promise. I now beg to give "Soda Crystal" the requisite information respecting the manufacture of this article on a small scale. The soda ash, or, as it is termed, "white ash," from which this article is made, may be purchased from any of the alkali manufacturers in such quantities as he requires, and if there are any in the vicinity in which he resides so much the better as regards his profits. In addition to the two pans, " Soda Crystal" will require a cistern to serve as a settler. If he has nothing better, let him get a large cask that will contain about 160 gallons, and let him provide this with a tap Sin. or 4in. above the bottom, the use of which will be referred to further on. "S. C." must also fix one of the pans over a fireplace, and the other must be left uncased, so that air may play all round it. In the pan over the fire water must be put iu to within 6in. of the top, and brought to a boiling heat, after which tho ash must bo thrown in iu email quantities until the density reaches 45° Twaddell, or thereabouts. Care most be taken when patting in the ash that it la kept continually stirred, so as to dissolve every particle of it, for unless this is attended to some of it will get into hard cakes, which it is difficult to dissolve. When this density la attained, the liquid is drawn off into the settler, where all the sediment soon falls to the bottom. In large manufacturing establishments it is customary to throw in a few spadefuls of bleaching powder, which facilitates the deposit of the sediment and causes the crystals to be clearer than they would otherwise be. The clarified liquor is now drawn from the settler by means of the tap at the bottom and conveyed to the pan again. The lire is urged, and the contents of the pan kept in a state of ebullition until the density reaches 64 Twaddell. It is then allowed to cool to about 90 Fahr.t when it must be run off into the crystallizing pan, or it may be allowed to crystallize in the same pan, but in this ease the crystals will take a longer time before they begin to form, on account of the heat in the surrounding brickwork. Iron rods must be laid across the pan, and just beneath the surface, on purpose to support the crust which forms on the top, and to which a quantity of purer crystals attaches. The crystals will very soon begin to form themselves, and will continue to grow until the density gets too low. When completely crystallized, the liquor, which is termed mot her-liquor, is siphoned ofT, and the crystals allowed to drain, after which they may be cut out with chisels and stored in a dry place ready for sale. The time occupied in the formation of a crop of crystals varies according to the state of the weather: in winter, or very cold weather, it takes about six days, whereas in summer it will require eight or nine days. The quantity of crystals obtained will be above double the weight of ash used. The mother liquor may be used again in making a further quantity instead of fresh water. "S. C." must not expect very large profits from the small quantity that he will be able to produce, but still I have proved by experience that as small a quantity as jewt. of crystals can be made for less than they can be bought from the manufacturers, calculating at the rate per ton. If " S. C." will take particular notice of the quantity of soda ash he uses the first time to bring H certain number of gallons of water to the requisite density, he will have no need to use any of Twaddell's hydrometers at all; to ascertain when the liquor is boiled up to ita c y=t:iili/.iug density, viz. 54J, let him take a small quantity in a ladle or cup, and blow on it with his mouth, when, if it forms a scum on the surface he may conclude that it is boiled enough. I trust that I have given the information sufficiently clear to be understood by " S. C." if not let him ask again for what is deficient.— J. Roskell. for your use add a little water; if too thin, place it on the fire, the water will soon evaporate.—Cabinst

[4532.]— TELESCOPIC, Etc.—In reply to " H. A. C," it cannot i airly be considered good work for an HHn. silvered glass reflecting telescope to render the satellites of Jupiter visible in sunshine. One of the satellites, tho 3rd, has been seen with only Sun. aperture, 50 minutes before sunset, by Mr. C. Grover. I have very frequently observed the satellites before sunset with a 4jiu. O. G., and have no doubt that the 3rd could be seen throughout an entire day with Bin. of aperture. Let your correspondent turn his telescope on -j* Andromeda and if he sees the components fairly divided he may be sure that hid telescope is a very excellent one.—

H-EHPERUS.

[4541.]— EMBROIDERING MACHINE.—The machine which I think will suit "A Braider " and recommend him to see is the " Excelsior," Whight & Mann, 143, Holborn-hill, price from £6 6s. It makes the double chain stitch the same as the Grover & Baker, with the advantages of a straight needle and a simpler mechanism. It has no feed, therefore the work can be turned right round with the needlo for a pivot. I have had one nine months and am quite satisfied with it. The work though quite strong unpicks readily.—O. E. R.

[4546.J — DIVISION PLATE.—" Wahsrof" evidently has not given much attention to this subject or he would not recommend such numbers as he does. For example, a man who has a circle of 780 hole* (who ever had 1) cannot possibly have any occasion for 300, 144, or 120. The numbers 221 and 209 are the most absurd possible, as one is 11 times 19 and tho other 18 times 17, and you cannot obtain twice or three times any of those numbers, as they are all primes, so that you have to pay for boring 430 holes, of which only GO are of any use at all, the rest not even for " fine rings or flutes." I must confess I cannot understand the lines against which he writes "divide into differences.'*—J. K. P.

[454C.] DIVISION PLATE.-I have a lathe by Holtzapffel and one by Buck, the division plate on the former contains the following 360,192, 144, 120,112 and 90, that on the latter 240,180, and 108.—T. W. Boord.

[4554.]—PENDULUM.—In answer to " Lex " I beg to inform him that it is not the simple lengthening or shortening of the stroke of the pendulum which regulates the clock, but the alteration in the length of the pendulum itself.—F. J. Walker.

[4556.]—TELEGRAPHY.—In reply to " Mus," I think the .band which he describes is to conduct the atmospheric electricity to the ground.—John Lego.

[4556.]—TELEGRAPHY.—In answer to "Mus," he is right in supposing that "A " in the diagram is to prevent the wire slipping off the pole. It is termed a "wire guard," but on all new lines a "hoop guard" is used, that is, a galvauised-iron inch-wide strap, arched over the insulator and fastened both sides. By the way, his diagram is quite wrong, he never saw two wires fastened to one insulator.—Terminal.

[4560.]—PAINTING CISTERN.—If your cistern is well scraped and dried, a light coat of red lead paint ought to remain good for years.—Vivis Sperandcm.

[4563.]— BRASS COIN—is a Nuremberg counter; observe tho letters RECHP. '* Rechenpfcnning" or counter; those letters are always sufficieutfor classing a coin among the German oounters. Tho present bears even the English word "Counter."—Bekxardxx.

[4568.]— COPPER AND BRASS COINS.—The first one is a Roman coin of the Emperor Probus, who reigned from A.d 276 to A.d. 282. It Is of the size called 3rd or small bronze. The obverse bears the crowned bust of the emperor to the right, circumscribed IMP. C. PROBVS. P. F. AVG. (Imperator Caiua Probus Pius

Felix Augusta*.} Reverse: a woman standing, holding a branch in her right hand, and a spear in her left. Inscription : COMES AVG. (Cornea Augusti.) Common, worth I'll, to la. The brass one is not a coin at all, but a common card counter, quite worthless.—Henry W. Henfrry, M.N.8., 4c.

[4564.]—TWO SILVER COINS.—No. 1 is a denarius of the Roman family of Antestia. Obverse: the winged head of the Pallas to the right; X for the value in front; and C. ANTESTI. behind (Caius Antestius). Reverse: Castor and Pollux on horseback to the right, with their lances in real. A dog running below. In the exergue ROMA. This coin is common, worth 2s. Coinod about 40 years B.C. The second coin is ancient Greek, but the drawing is very indistinct.—Henry W.henfrey, M.N.S., Ac, Ac.

[4573.] METHYLATED SPIRIT.—In common with every other article of commerce methylated spirit varies in quality with the price, or dishonesty of the vendor. The commoner kinds contain considerably more than the regulation qoantity of wood naphtha, and again, the wood naphtha naolf contains a greater or less amount of tarry matter, according to the purification which it has undergone. The well-known empyreumatic odour of methylated alcohol is due to the presence of tar and other product* of destructive distillation.—An Associate Of Royal School or Mikes.

[4577.] INDUCTION COIL.-The inductive effect of a magnet is greatest at it? middle, heucc, as "Inductoriuni" stated, that of the coll is so because it depends upon the magnetism of the core: The partitions do not waste the power as**Opernlor"fnpposcs, because they are not addition* but tubstit ;it ion*. They are sectional or vertical insulator! rn place of the ordinary horizontal ones. I consider good paper soaked in paraffine better than gutta-percha tissue of tho same thickness. As I have several times said I have not had such experience in making induction coils as to justify my going into such details as are a iked for, though I have made many of the coils aw fitted for medical use, and have described them. I only make instruments for my own experiments, and induction colls are somewhat serious affairs, and have not, a? yet taken up much of my attention.—SlttHA.

[4579.] DUTIES OF GAS ENGINEER.—These are very extensive, and vary very much with the size of the works. In any case he has to keep up good discipline. To watch the .quality of coal; the perfect state of repair of all the works ; to decide upon the degree of heat and duration of carbonisation, Ac, all of which can only be acquired by experience based on knowledge. This latter should be a moderate acquaintance with chemistry, and the qualities of materials. In large works tho ordinary knowledge of a civil engineer is needed, such as relates to strength of materials and forms, as well as the principles of construction, and a good acquaintance with mechanical drawing. There are many books upon the subject, of which perhaps Clegg's is the beat. Bowditch's are useful, and Hughes is a hash-up of a compilation published in Weales' series : I do not renumber the titles, and have no list at hand.—Sioma.

[4582.]—GOLD LEAF.—Gold books are rubbed with red chalk, or crocus powder, I believe, bat it in done to prevent the gold leaf adhering to the paper, aud not, as "Ohcniicus 'supposes, to prevent its flying about. The leaf is nearly always laid on the gold cushion before being applied to the work to be gilt. There are four methods of lifting the leaf from the cushion. 1st. A piece of thiu beech, called a triudle, is rubbed on the workman's head, and then applied to lift the gold. 2nd. A piece of stout paper. 3rd. A gilder's tip. 4th. A piece of cotton wool.—An Initio.

[4580.]—TENDER FEET.—I think J. T. Hill will find relief if he turns his stockings inside out, and rubs them well with a piece of soap nul-itcned in water. Boots with thick soles are not so apt to blister the feet as thin ones. Blisters also sometimes arise from boots being much too large. Tight boots also have the same effect. —W.

[4590.]—TOWN GARDENING.—"A Factory Lad" will not succeed in growing geraniums and fuchsias anywhere if they are exposed to the fumes of burning gas. Notwithstanding the purification which gas now undergoes there is still too much sulphur in it, aud plants of any kind exposed to its effects cannot thrive, and will scarcely live. If " A Factory Lad " will accept my advice he will not attempt to grow anything from seed, but will go to a gardener or a nursery, and buy what he wants just as they are coming into flower, or at any rate when well established. Wallflowers, sweet Williams, stocks, asters, and numerous others will bloom almost anywhere if well grown before removal. If, however, he icilt try seed, let him get Collinnia bicolor, Lupinut nanu*. Etf$imum PerojffkiaHuin, Nttnophila insignu, Virginia stock, larkspur, convolvulus, candytuft, and some of the other hardy annuals. I have seen these blooming even in London areas, where they get very little light, not to mention sunshine. When the seed comes up leave only two or three in a pot, so as to give them room to grow. Geraniums and fuchsias I have seen flourishing in London windows. Sunshine is not a uecessitv, but they should have as much light as possible. The creeping jenny does well to hang down in front and hide the boxes. Above all things give the plants good wholesome mould, such as turfs cut from a meadow, liin. thick, and crumbled up with a little sand if necessary. Always keep the leaves clean by syringing or watering, as they act as lungs, and town son and dust soon block up their pores, and so " choke " the plants.—Saul Rymra.

[4592.]—CHANGE WHEELS.-I think "C. C." had better beg, buy, or borrow Binns' second course, and read therein the chapters on wheel teeth. The scriber for striking tho epieycloids is always a portion of a eirclo of one hah the diameter of the smallest wheel of the *et, which Willis puts at twelve teeth, and Binns proposes to make fourteen the universal standard for, as it makes a better shaped tooth, the wheels will then interchange anyhow. If the wheel i-» always to drive the pinion, as in clocks, and supposing the pinion to be a lantern, then the scribing circle requires to be the whole diameter, instead of half the pinion ; but as the pinions of clocks are commonly only half tho size of those used in other machinery, the result in much the same tooth for the wheels iu either case. Where a wheel is always driven it requires no top to tho teeth, which may all bo turned off down nearly to the pitch line, and consequently the

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MAKER.

[4609.] MELTING GLUE.—Soak a cake of glue from 12 to S4 hours in cold water, theu drain off the water, put it (the glue) in the glue pot, fill the outer vessel with boiling water and apply heat. The glue will speedily run into A liquid ill for use. Tho longer it is soaked the more liquid it will be. Gluo improves in quality by frequent melting.—J. W. Boord.

[4608.1— FISHING.—" Mr. Jamieson" will And plenty

of bleak and gudgeon in the Lea, cither at Rye House,

Tottenham, or Temple Mills; but he must remember

tliat gudgeon swim near the bottom and bleak near the

surface. A good method of angling for bleak is to have

ii. light fly-rod and line, and a No. 1 hook mounted on a

bit of the vory finest gut, stained greyish green. About

11 or 2ft. from the hook place a round piece of cork,

about as large as a good-sized pea, which will do for a

float. Bait with one nice large gentle, and have ready

some bran, mixed with sufficient water to cause it to

Adbere on pressure and yet to crumble up readily when

thrown into the water. Choose a likely spot for a swim,

which is caBily discovered by the bleak rising, throw a

handful of bran up stream, and drop the baited hook

on the water, letting it float down with the bran till you

get a bite. This is considered tho best method, but

bleak can be taken with anything, only you must fish on

the top. They are found in most streams producing

dace and roach; and gudgeon are to be caught in nearly

every running riverin the kingdom. Stone-loach are to be

found underneath stones; and the best way to catch

them, is to wade into the water, remove the large stones,

and net or spear them. Thames fishermen always rake

the bottom when fishing for gudgeon; this is as good as

ground bait, or better.—A. T., Staines.

[4604.]—PICRIC ACID is formed by the action of fuming nitric acid upon many organic substances containing nitrogen, such as silk, indigo, salicin, <fcc, &c„ but more cheaply by treating carbolic acid and its derivatives with nitric acid. It ia a bright, yellow crystalline substance, possessing great tinctorial properties. It dissolves in about 90 parts of cold water, to -which it imparts a yellow colour, and a bitter taste; it is on accouut of this latter property that it has been substituted for hops in brewing, although, from what I can glean, more importance has been attached to this means of adulteration than it deserves, for it is not so commonly used as is generally supposed. A test which can readily be applied by persons not conversant with chemical manipulation is to take a skein of white silk, and allow it to remain in the ale under trial for a short time, when, if there be Any appreciable amount of picric acid present, the silk will be found to have acquired a yellow tint. Another test is to shake the ale well until a good froth is obtained; this, if the acid be present in any quantity, will have a yellow shade.—An Associate Ok The Royal School Of Mixes.

[4604.]—PICRIC ACID.—Picric acid or tri-nitrophenic acid, one of the coal-tar dyes, of canary-yellow colour, and very bitter taste. Its tinctorial power is very great, one part distinctly tinging 800,000 parts of water. A simple solution in water is sufficient to dye animal fabrics a fast canary-yellow, although it is generally applied with alum and tartar. Its use as a substitute for hops is objectionable, as It is said to yellow the eyes of those who partake of it. It may be'easily detected as follows :—Take a sma 1 test tnbe, say 4in. by 3in., half fill this with the liquid to be tested; add a small bit of potash or soda, about the size of A grain of wheat; warm this over a gaslight until dissolved; now add a small crystal of green copperas; hold the to^t tube up to tho light, and watch the change of colour; if picric acid be present the liquid becomes a reddish brown, but If not present, it becomes a dirty greenish white.— Crow Trees.

[4604.]—PICRIC ACID.-This acid is formed by the action of nitric acid on indigo. Brilliant yellow Bcales, very bitter and highly poisonous; used in dyeing yellow, its salts are mostly explosive with boat. It throws down a yellow crystalli Ip precipitate, solublo in water, with caustic potash.—J. W. Boord.

[4605.] —PROPELLING A VESSEL BY A WINDMILL. —A vessel could not be propelled head to wind by a windmill, for even supposing friction to be put out of the question, and the whole ot the power exercised by the wind on the windmill to be utilized by the screw, the result would simply be that the vessel would remain stationary; but as more or less of the power would be lost on account of the friction of tho machinery, and as the wind would moreover be acting on the'hull and rigging of the ship, the practical result would be that the vessel would go backwards instead of forwards, though not perhaps so reAdily as if the machinery were not at work.—W.

[4607-3—ORGAN BUILDING.—To make stop diapason speak louder. This can bo done—providing the scale will admit—by " cutting-up" the mouths of the pipes higher, as well as by taking out the plugs, which arc sometimes put by the builders into the feet to soften tho tone by reducing the supply of wind. This requires considerable experience to do; and unless "W. Porters" is a first class hand at voicing I should recommend h>mt<» takehisstop to a regular organ-builder, who will, if the thing is practicable, very soon do what he requires, whereas hiH own efforts may only render his stop uneven and perfectly unbearable. As regards hardening brass wire lor^pallet-springs, don't have an inch of it in an organ at all, unless you wish to have a constant source ol annoyance in the shape of repairs. Steel and tralVAnized iron wire are almost universally used by builders for pallet-springs.—H. T. R.

[4611.1 -POLISHING VULCANITE.-" G. N. L." crui get a perfect surface on his vulcanite by removing the scratches with a smooth watcrayr stone (wet), aud then 811,]n?.ll." 8°°^ Ponuclng at his lathe with fine pumice and stiff bruin. After washing the pumice off he can polish it with whiting and soft brush. He must keep turning his work about in different directions, so an not to keep brushing- in ono direction, for if he does, he will never get a surface.—J. C. P.

t^J-ELECTROLYSIS. — This can be easily effected by an electro-magnetic apparatus, if arranged to give a "quantity" current, and in one direction only, lao ordinary instruments sold would be totally useless,

As they Are arranged to give a current of high tension or Bhocks, Instoad of quantity.—Sigma.

[4618-]— MANAGEMENT OF BEES.—The best boofeeder is a wide-mouthed glass bottle holding about U pints. Half fill with syrup and tie a piece of coarse cloth tightly over the mouth, plAce a piece of wire gauze over one of the openings in tho board forming the top of the hive. And turn the bottle quickly upside down placing it at once on tho gauze. Last winter my beeB consumed about a pint in ten days, as nearly as I recollect, but they had very little stock honey in their hive. The bottle, complete, may be had at Neighbour's, Re gent-street.—J. W. Boord.

[4621.]— CHLORIDE OF GOLD.—Dissolve the gold cuttings, which should not be too large, in aquaiegia, this should contain more hydrochloric acid than nitric ; evaporate down on a water bath, when a red deliquescent mass of chloride of gold will remain. If a pale yellow powder be left on taking up with water do not throw it away, for it is the sparingly soluble protochloride of gold. The readiest way to get rid of this is to ignite it and re-dissolve tho metallic gold thuB obtained in some more aqua regia, and proceed as before. —An Associate Of The Royal School Of Mikes.

[4&J1.]—CHLORIDE OF GOLD.—Dissolve the gold in aqua regia and evaporate to dryness over a water bath. The residue may then be dissolved in water.— Exhibitioner At Royal Colleoe Of Science.

T4631 A 4622.] CHLORIDE OF GOLD AND NITRATE OF SILVE it.—Chloride of gold, or more properly terchloride of gold, is made by dissolving pure gold, one part, in three parts of nitro-muriatic acid (composed of nitric acid one part, and muriatic acid two parts); when, by the (assistance of heAt, the solution is complete, evaporate until fumes of chlorine are disengaged (to be distinguished by the smell) And set aside to crystallize To utilize your old solution of silver add a solution of common salt in excess, i.e., until no further precipitate is produced; collect the chloride thus produced on a filter, wash and dry it, then throw it carefully and by small portions into a red hot hessian crucible containing twice its weight of fused carbonate of potash with a little borax, waiting until the effervescence oeases each time before adding a fresh quantity ; when all is in raise the heat considerably to prevent the silver from adhering in globules to the side of the crucible, and allow the whole to cool slowly. The silver thus obtained may be dissolved in nitric acid and crystals obtained in the usual way. The salts obtained in both the Above processes should be re-crystallized twice to insure purity. Cuttings of paper filters, <£c, containing silver should be burnt, the ashes treated with nitric acid, and the resulting liquid as above.—J. W. Boord.

[4622.]—NITRATE OF SILVER.—Do as you say. Evaporate down to dryness; powder it, and mix with some oarhonatc of soda, as a flux, and a little charcoal powder, and then fuse.—An Associate Of The Royal School Of Mines.

[4627.] — DISCOLORATION OF LEATHER. — In tho process of tanning, leather is made to take up tannic aud gallic acids; these combine with iron, derived from the metallic surfaces of the press, and form tannate principally, and some gallate of iron, both of them are black, hence the stained leather; in fact black ink is formed. This discoloration may be prevented by not allowing the iron surfaces to come In contact with the wet leather. Would it be feasible to apply a thick coat of paint to the presses and so prevent direct contact between tho two?—An Associate Of The Royal School Of Mines.

[4627.] DISCOLORATION OF LEATHER.—When the iron-mould comes into contact with the leather, which contains tannin, a combination is formed similar to that which gives its colour to ink. If the moulds and leather were perfectly dry this would not take place. Brass moulds would not be open to the same objection. —J. W. Boord.

[4637.] — DISCOLORATION OF LEATHER. — "G. A. G." is certain to get his leather discoloured while he nses iron upon damp leather. Cannot he use boxwood or something similar ?—Ab Initio.

[1631.]—LATHE.—TO H. WILLIAMS.—I should sny No. 12 gauge-wheels would do very well. The size of screw may be lin., unless it is a very long one, in which case it is desirable, I think, to have a bearing close to where the thread terminates on the left of the gap. Of course the smaller the diameter of screw the less the force required to work it, and that is considerable when you are cutting a screw of high pitch. I may as well take this opportunity of stating ray firm opinion, that in this case, as in most others where screws are used for any purpose, except as what Holtzapffel calls the "cement" that binds portions of machinery together, a very great economy of force is obtainable by the use of a high-pitched screw. And for your case one of lin. pitch and lin. diameter, would, I am quite positive, give a most satisfactory result in working. It would bo, perhaps, 'difficult to get cut, and still more to get a nut made fbr it; and is moreover so at variance with usual practice, that I should not advise you to act on my opinion, however firm it may be, as I have not tried such a screw yet—though I have everything nearly ready for doing so. Yon might safely have one of £in. pitch, with a 4in. threAded screw, cut with A No. 8 sorew-tool. I itdvocAte the plan of making the screw in two pArts, viz., the plain part at the left-hand of the la tho terminating in a socket, into which either end of the screw may be keyed, a portion of the thread, say an inch at pRan end, beiug turned away for the purpose. Close behind the socket comes the extra bearing I propose

ibove, and then you may safely reduce the diameter of pour screw. I should strongly advise you to send your screw to Wilkinson, No. 43, St. George's-road, London, to be cut, as you will then have it of a true number of

breads to an inch, which is commonly not the case in lithe screws.—J. K. P;

[4633.]—SILK WINDING.—The cocoons must bewail tteeped in a warm soap-lye, and the ■(— taken < ft" un' i' Lhe fibre will run easily: then five or six of the fibres are iken together, passed through a small eyelet, or guide, ,md wound upon a large reel. As soon as any cocoon oeoomeg exhausted orruns down to a mere skin.it must, be replaced by a fresh ono so as to keep the reeled 'bread uniform ia thickness.—Crow Trees.

[4G40.] — SOUTH KENSINGTON EXAMINATION PAPERS.—These papers are to be hAd of Messrs. Chapman & Hall, Piccadilly, London, stitched together in batches of four or five different subjects, prioe about 3d. or 4d.—Crow Trees.

[4641.]—MILL BILLS.-" R. D." can get his bills to stand if he is careful not to heat them beyond a bright cherry-red when drawing down the points. The process requires skill, no chemical being used in the water. Begin by carefully aud regularly heating the point to be first drawn, and sledging it down to about one-half more than the intended thickness, tapering it in width so that when drawn by the hand-hammer to the proper thickness it is of equal width throughout, as hammering the edge now will cause the corners to fly. After cutting square, and flatting tho point, thrust the bill through the fire and heat well up before attempting to heat the end, turning it round so as not to burn tho edges; draw the point into the fire aud heat toa brightish red, being careful of the corners. Harden by plunging about Sin. of the

?oint perpendicularly into a pailful of cold spring-water. f " R. D." accomplishes all this skilfully, being sparing of heat, though not of labour, his bills will stand dressing the hardest millstone.—T. A.

[4641.]— MILL BILLS.—u R. D." should use yellow

Erussiate of potAsh, and plunge into urine, while red ot. As far as my experience goes, that never fails if the metal be good.—Ab Initio.

QUERIES.

[4645.] —HYDROGEN LAMP.—I have a hydrogou lamp which is minus tho platinum. I went to Jaoksou A Townson's.and asked for a bit of spongy platinum, and was told that it was a powder. The receptacle for it is like A sin nil thimble turned towards the jet from which the hydrogen issues. Will some one inform me how I am to proceed to put it in working order?— F.R.M.S.

[4646.]—MAGNETO-ELECTRIC MACHINE.—Would some kind brother reader inform me if any experiments can be performed with one of these machines apart from their ordiuary medical use,—if so, I should like to know what and 'how to be performed—so as a number of porsons could see it at one time? or if by any means the current of electricity oan be made more powerful? Would a coil of wire or helix add to tho strength? Tho answer of some reader will oblige.—Enquirer.

[4617.]—PHOTOGRAPHIC—TO "MUS," OR » OPERATOR."—Will either of the above gentlemen kindly assist me in the following matters ?—1st. By mistake I mixed the nitrate of silver in. filtered *o ft water. Does it matter? If it does, what had I better do? 3nd. In looking on tho focus screen, the figures (houses, pigconhonse, saw-mills) are not only upside down, but reversed (saw-millson left hand, Ac). I don't think the latter position can be correct. If it is not, how Bhall I alter it? 3rd. I can get no image on the plate when the developer is poured on. What is the remedy for this? I have taken the English Mechanic regularly for several months, but as I do not see any information applying to my case, I have acted on " Mug's "advice to another correspondent and beg leave to ask for it.—Mendicds.

[464a]—TWO COINS.—If any reader of the English Mechanic would inform me through the modinm of your pages the value and other particulars of the two

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coins in my collection of which the above are akctche3, they would greatly oblige.—Constans Lector.

[4649.]—FRICTIOXAL ELECTRICITY.—I have a cylinder electrical machine, the cylinder (longth lKin., diameter Sin.) being supported on two brass pillars screwed into a brass table, into which is also screwed tho brass spring to which the rubber is attached; and would esteem it a favour if any reader would kindly explain why I can only get a lin. spark from the prime conductor (which is mounted upon a separate glass)? —patty.

[4630.]—FRENCH LANGUAGE.—Would any reader favour me with the name of a first-class book from which an English person might study the above, also the cost and publisher?—Patty.

[4631.]— POWER OF WATER-WHEEL.—I shall fee! thankful if any or my fellow-readers will kindly assist me with a plain rule to find the ho rse-power of an overshot water-whoel, diameter 16ft., breadth 4ft. Also, would a penstock of 8ft. or 10ft. above the whool increase its power and also its velocity? If so, in what ratio ?— Miller.

[4652.]—TONING BATH.—I am often troubled with my toning bath not working well. Would any of your readers oblige me with a good, trustworthy formula, giving good uniform tone? I think " Mas," " Operator," and others can supply me with sound information.— John Terras.

[4633.]—SUNDIALS.—One of oar friends, "E. L.O. * [4131], says sundials can be easily made to show clock time throughout the year, by having two gnomons used alternately for nearly half a year each. He leaves the problem to be solved by your readers. As unfortunately the problem is beyond my ingenuity, I shall feel obliged if he will favour me with further information.—Sundial.

[4654.] — OCCULTATION OF SATURN. — Will "F.R.A.S.," Mr. R. A. Proctor, or some other correspondent, kindly explain the following ?—It is stated in the Nautical Almanac that the planet Saturn id occulted by the moon on the evening of the 30th September. The disappearance is predicted to oocur at 6h. 4ni., and the r,-appearance at 7h. 18m. So far this is perfectly clear, bat on referring to the "Elements of Occultation, in the same volnme, I find that the planet will be in conjunction with the moon at 6h. 12m. on the same date and that at the time of conjunetion the planet will be situated 56m. of arc distant from onr satellite. How can this be, when at 6b. 12m. the planet will be actually occulted by the moon ?—Hesperus.

[4655.]—MANGANESE BATTERY.—I have seen Mr. Stone's reply to "M. D." in the last number, regarding the manganese battery, and I am very glad to hear they answer so well. 1 wish 1 could say that two cells I use for bell-ringing,had gone untouched for as long a period. The fact is thai in my case the connections of the battery corrode, so that I am obliged at least once a fortnight to disconnect, and file binding screws, Ac, until quite bright. This is the only trouble I have with the battery, mid surely if it will go fn one case months without any attention, it will in another. Perhaps Mr. Stone will save me a hint or two on the subject,espeeially as to some less rough process of cleaning the connections, which at the rate I file them will soon bo worn out.—E. H. B.

[4655].—GOLD COIN.—WiU Mr. Henfrey or some numismatic friend kindly inform what the gold coin is.

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and tho value, of which I send the exact sizo and copy? Hoi" °n °"e 8ide' Wcisnt 2 dwt- w grs.—Henry

w[4?7'J r KNOT-STITCH SEWING-MACHINE.— would " Practical Hand," or some other brother reader, uinaly answer the following? I want to make a knotted-trtcu sowing-machine, but do not quite understand now to moke the loopcr, nor yet the length of stroke the needle should travel.—J. 8. 8.

[485a] —CLEANING GILT FRAMES.—I should bo glad to know the best way to clean the gilt frame of a chimney glass. As it is not of recent (cheap) manufacture, 1 Unnk the gilt will bear operating upon. The gilt is not damaged by accident, bnt is of a smoky appearance, and being highly ornamental will cost too much toregild.—W. E.M.

[4669.J-TURNING HARMONIUM INTO AN AMERICAN ORGAN.—Could Mr. E. H. Jones (who wrote relating to American organs) tell me if I could make or alter an harmonium into an American organ ?—J. W.

[4660.]—WELDING FORKS.—Would some reader be so good as to state the process of welding cast-steel, such as theprongsof forks, Ac ?—J. W.

[4661.]-CATERPILLAR.-Will some reader of the r.ijomsH Mechanic inform me what is the name of this caterpillar 1 It has a broad white stripe down the back: a. horn on the third segment, black; broad black stripe down the sides, which is marked dimly with orange; head and claspers black.—J. Hampton.

[4663.]—COIL.—I have made an induction coil with jib. No. 16 primary wire, and lib. No. 86 seoondary wire, 9in. long. How much battery power can I use with safety, and how much spark ought I to get without condenser 1 How long a spark oan I expect from a single i pint bichromate battery ?—Tometer.

[4668.J-BRAKE PIECE.-Can any one favour me with a description of a brake piece that reverses the current of electricity suitable for a coil 1—Tometer.

I46**-!-PRESSURE 0F WATER.—Can any reader of the English Mechanic tell me if there is any difference in the pressure of water at the bottom of two pipes, both 12ft. high? One is 4in-diameter the whole length ; both are vertical; the othor 8in. diameter for 8ft of its length, the bottom 4ft., are 4in. diameter. Is there any difference at the bottom of the two pipoB in pressure per square inch ?—Holbecx.

[4665.]-PROBLEM.-Would any reader give me a solution of the following problem, taken from the first B.A. Algebra paper, London University? o. "An express train which ought to travel at uniform Bpoed, after being an hour in motion, was delayed half an hour by an accidont; aftor which it proceeded at three-fourths of its original rate of speed, and in consequence srrivod at the end of its journey lh. 60m. behind time. Had the accident ocenrred (and the same delay and subsequent retardation taken place) after the train had boen an hour and a half in motion, the train would have been Ul. 40m. behind time. Find the length of the line, a. Supposing tho above question were varied in the latter part of it by your being informed that 'had the accident occurred when tho train had gone half-way, it would ha^e arrived lh. 20m behind time ;' would that information have boen iucerrect?" Would it have enabled you to dotermino tho length of the line."— Beverley.

[4660]-LIQUID BONE MANURE.-I shall bo obliged ll some of our correspondents can toll mo how to dissolve boues, sn as to make a liquid bone manure which may be used without injury to plants ?—S. W.

[4667.] -CLFANING GUN-BARRELS.-Does " Muzzle

Loader" recommend fine emery-paper for cleaning gunbarrels every time that they get foul? I should imagine that it would wear them much more than tow wrapped round the cleaning-rod would.—Nebdlkgun.

[4668.]— THE LATHE.—TO "J. K. P."—I am just

going to hove a 4,in. oentrelathe, with back gear, ovoread, and screw-cutting motion, and do not exactly know how to get it: whether I must buy it complete of a maker, or if I could get the castings and have them planed up, and do all the other part that I can myself, and put what I cannot do out to a latho-maker to be done, such as the leading screw, Ac, Ac. I have enquired of a great many lathe-makers tho price of such a lathe (first-class work, and all the borings hardened steel), and find that some, such as Evans, say about £100, and others gradually lower in price down* to £25, which is the lowost estimate I can get. A man in Compton-streot, Clerkenwell, offers to make it for that. Now, I consider that £25 is a fair price for this kind of lathe without any chucks, but from what I have heard the higher-priced makers say, I shall not get such a lathe as I expect for that money. The mandrel will be iron, case-hardened, and all the borings of the same material, which would never suit me, as I want this lAthe to last me a life-time, if used with caro, as an amateur would nse a lathe; besides I have not got£70 or £80 to lay out, end it would take me yean to save so much, and I want tho lathe with as little delay as possible. If, on the othor hand, I can get the castings, and have tbem planed up. for about £6 or £7 (the lathe-makers estimate them ready planed at from £10 to £4 10s.) I ought to get a very gooJ set of castings to work upon, and I think that as I could get through a great deal of the work myself, got the long leading sorew cut by a lathe-maker, also the slide-rest screws, and have the pulloy divided, Ac, Ac (I could fit thorn in their places myself), it would reduce the cost very considerably—as my time is my own, and, therefore, should not be reckoned in the expense. I have a very good Gin. latho, 3ft. 6in. bed, with slide-rest, face-plate, and chucks, audi know how to use it perhaps as well as the general run of workmen. Could I on this lathe with my experience, make an attempt with any chance of success to make the kind of lathe I have endeavoured to describo in this letter, or, at least, the greater part of it? Will "J. K. P." kindly say what I had better do under these circumstances ?—Tometer.

[4669.]—OXYHYDROGEN MICROSCOPE.—Can I use my achromatic microscope lenses (lln. and itin.) with an oxyhydrogen lantern, 8Jin. condenser, for showing microscopic objects on a screen? A description of the mounting required would oblige, if possible.—E. n. Jones.

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[4670.J—SATURN.-WU] any subscriber kindly inform me what part of the heavens to look to to find Saturn, and tho same for Jupiter, about from eight till ten in the night 1 Please to name the constellations they will be in about tho time your reply will appear. I looked for Saturn for weeks, but not knowing in what part to look I have not succeeded in finding it.—Young Amateur.

[See "Astronomical Notes," by " F.R.A.S.," in this number.]

[4671.]—ICEBERGS.—Can you or any of your readers say why icebergs were met this year (1870) on the banks of Newfoundland in March? They must have loft Baffin's Bay before the sun was seen there. Could they have been detached by an earthquake ?—C. J. R.

[4672.]—KITE—Suppose a large and well-proportioned kite to be properly balanced and inclined in a favourable wind, being free from all direct attachment with the earth, and also the common appendages, would it mount, and if necessary, on a change of inclination, make progression against the said wind by the virtue of the aforesaid counterbalance being dependent from a proper position to some distance beneath, and the inclination being rigid? A speedy reply will much oblige.

[4678.]—INDIAN COIN.—I shall be much obliged if

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any kind reader will describe the Indian oopper coin, of which I forward sketch.—Collector.

[4874.]-PROBLEMS.—a, through a point given in a circle.draw a chord which will be cut by the circumference in extreme and mean ratio at the given point, b, same problem, an angle being substituted for the circle,—X. Y.

[4675.] -POND FOR GOLD-FI8H.-I have a pond in which I keep roach, gudgeons, and minnows. I am about to put gold-fish in it. Shall I be able to keep them alive all winter, or must they have protection ) If so, what way should I proceed to afford it them? The pond is fed by a spring-water pipe, and is about 20 yards square, and 6ft. deep.—Vlvis Speranduk.

[4676.] —NITRATE OF SILVER.—I have a quantity of nitrate of silver precipitate, thrown down with salt from photographic slops. Would some reader kindly tell me how to re-dissolve it, so as to be perfectly neutral and fit for either bath or exciting paper ?—Paddy.

[4677.] —WATER POWER—Would any brother reader inform mo what power I could get from a fall of water fifteen feet through an inch pipe, if applied to a turbine wheel? And what size, Ac, of a turbine would do? Also what kind of a turbine would be beat?—A Regular Subscriber.

[4678.]—BOURNE ON THE STEAM ENGINE.-I am about to purchase a work on the steam engine. Is there a better work on the snhject than Bourne's? If there is would one of your readers tell me tho price, publisher Ac. ?—Thos. Watson.

[•4079.1 -CIVIL ENGINEERS' EXAMINATIONS.Would some kind correspondent give me a little information about the Institute of Chil Engineers? What is necessary to become a member? and y\h:il is rc

if cast on how is the cylind\«r finished off.'
I put anything in my crucible (brass) ts _
free in casting, and how to avoid the sender*.
going in with it, as it chokes np the mould-;«
moulds require to be heated? Thanks to-1.Os
his last instruction on cylinder: —AmTrfia
Founder.

[4684.]— TYPE.-Would airy reader »e iiail is»V' inform me whether there is any decisive t«-tti tinguish "pirated " from genuine "fj«a " in rr»» whether, if in equal quality of metal, the ic-rnrnt. serviceable to the printer ?—Country Prlstek.

[4685.]—GILDING KLECTRO.-WB1 same pndh electrician give me some informatiao spun »fc»t' known to the trade as solid depositing—1/„ ■»«'»'?turing solid articles by depositing gold in to* «? Lki copper is deposited? la the solnuan wurkf-j asm «■ cold? What battery power is used, smaeed Itv asiorir; or intensity? What is the right prvporvan ,*,' toe Areas exposed of the anode and the eataadr." Bait is tie best surface to deposit upon? / Better? there reasj Se a large quantity of gold in tie ssiaaua.—W. & Cemx.

[4686.]—INSULATION.-TO - DTDTjCTOEinnf-I wish to ask "Inductorium," woo otsauiei % mote of making a coil on page 472, Sa, Yu,uta<u>As\?&tBisalation between the primary aao. secraaftr* e<-*\£ii& cient? In coils of the ordinarv ctiuArac'aoa oLk 4 small part of the seoondary circuit «u&t>jm^ tfl* primarv, being the layer next to the reel. lnUttTgvnl mode the two extremities of the secondary Mil&re«n> rated from the primary by only the thickness fci 'it reel, and from communicating with each taker Vy taw that thickness plus the resistance oi the phroirr t* tween tho two points. In his case the terminals ire 0sulated from each other by their silk covering tvwr tat thickness of the reel, and one of the rings plus uielae?) of the primary with its cotton covering. ToiJ loweri to only jin. solid ebonite, the rest of the re^ns certainly being not equal to Jin. of the same. Illi»« ebonite enough insulation between t he termiatk 4» wire giving Sin. and 4in. sparks in air f For his aal certainly hope so.—W. H. Oorrtx.

[4687.]—" PANCREATINE" AND "PANOMSE EMULSION."—The above preparations are &x«esia^ mediesfor indigestion, and are very aaelaltortsiia^ cod-liver oil, but to buy them comes expensive, if reader would inform me how I could prepare sai should foel greatly obliged.—H. H.

[4888.] -SEPARATING BEESWAX FROn MS Ac—I should feel greatly obliged it anv reoJ.fr c-ii form me how to separate beeswax from rtsin wi W foot oilwith which it has been mixed?—CjLBlsxr-xita.

[4689.] -PEDOMETERS.—Would any brotinnr.' give me a description of the action of the peooa«fAn Enquirxr.

[4690.]-HOROLOGICAL.-Will some of on » logical friends who are adepts at thu rxso of 1st HO give me some practical instructions how lu»f ceedin turning down the collet of a verjre loriu** the balance? What kind of bow am I to use-it'** strength, and string—also what kind of Kr»w»?' use; size of cutting angle it must have, portife-* hand in using, length of stroke for tho bow naitf" speud to suit best; and, above all, whether it ■•«•"* cut with the work revolving to the graver «• *** graver? I find in practice that I caaxiot ■»*£ progress when I attempt to cut the work n^a"7 its upper snrfaco towards the graver. All a*l»*^ appears to be a raers tcrapt. But in tho nftr- *"**' when the under surface of the work r« volrti «*■* the graver I make better progress. In fact IV**1*" unoutly taken hold enough to brtak the nrx >• «* Where is the fault, is it in the bow, the xfraver ** self? My friends may judge for themaelve.'sil"' progress when I tell tbem that it will taJce me Jj a*9 of hard cutting, scraping, and scratching to turn**-the collet of a polished verge, previona to putnsl* the balance when an adept could do the Mi,,,. »or»t half an hour. I also wish to know how the pi vota oi Apinions are got to the required size. Are thev tor* with the graver or filed dawn! I have frequently po"' new pinions, but always file them down to the reJoln Mzc in the turns, by placing the end of the pinion M notch at the end of tho centre of tho turns with I! end of the rest as a guard, to keep the edge of thet from running away from the shoulder of tho pivot it tho proper way ?—Scrape.

[4691.]_POWER OF ENOINE.-Would "Vertuir nus give me the power of an c.ugine whose cylinder I 'Jin. in the bore and of -lin. stroke, by the rnlc he m»^ tains in your last week's issue (4474), and what will ti the necessary thickness ot boiler plate, and pressure of steara to work at to attain tho power of one horse'

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