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bat gain 12-candle gas; according to Dr. Frankland they give 1*2-1, that is they have fulfilled their agreement, and it is travelling ont of the question to say that under other conditions other cities have better рая. The real truth, however, is that only on very rare occasions is the gas anything like this, and the average is probably over 13 candles, and in no single instance that ever I heard of has the gas ever been, as stated, 9 candles, unless absurdly burnt.
Such an assertion as that the gas now is worse than it was years ago is really too absurd. The only real basis for it is an apparent increase in tho quantity of sulphur, while there is really a great decrease; but within the last few years the process of testing has been so greatly improved that what previously passed undiscovered is now detected, as the gaa referees appointed in tlie interest of consumere pointedly show, and thus as fast as the companies succeed in removing more impurity, so previously unascertained impurities are presented. The bestauswer isthatitp<i¡fi to purify t as the impnrities, when collected, are valuable and saleable matters. Sigma.
ELECTRO-MAGNETISM AS А MOTIVE POWER.
 Sir,—Many people have endeavoured to utilize electro-magnetism to work machinery, and it is easily accomplished in many ways, but 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 this is quite possible, us 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. Bnt 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 uot yet carried that extent far enough. His idea that a coal fire is an electrical battery, is thus only a partial truth, though a favourite notion some time ago, before the grand doctrinos 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 up quiescent to be again set free, is governedfby the conditions of each cose. But let me beg *' Thinker" to cast away all notions as to " electricities uniting" to cause 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 we 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 the ores of zinc, a much more expensive procès than the exactly similar one of reducing what we may call the ore of carbon, i.e., carbonic acid, by heat from the нип and storing it as wood and coal. The economy of electro-magnetism as a motive force depends, therefore, npon 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 eloctro-magnet requires time to develop force; although the current generates magnetism in an infinitesimal period, the full 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, tho power developed by the battery is used up in producing molecular changes, passes into heat, and is lost, instead of into magnetic power and motion. Sigma.
 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 my excuse for tronbling the readers of the English Mechanic with a long dissertation upon education. The topic has lately and will be again in the minds of every one. Unfortunately a great calamity has fallen upon the nations of tho earth, and the surprise and consternation created hy a dreadful war erases every other subject for the time being from the tablets of our memory. The Quakers are right; it is inhuman and barbarian to lead onr fellow-men to the shambles for wholesale slaughter. Let our cry arise compelling the great ones to submit their differences to arbitration,
and let us determine to evade to the ntmost being drawn intoft sanguinary war, declared for no earthly reason except the Ambitions designs of one or two man. Hut I must not allow myself to be led into a dedacuitory essay upon war. Tikis is uot the time, not the place, for such a subject. Theremin of every Englishmaulshonld he to seek the welfare ef his nativo country; but in order to do this we most know exactly what she has, and what is wanting. Very tritely n contributor to Nature summed up this 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 England as regards these subjects. Edueatlon may conveniently be divided into three kinds: a Primary, ß Secondary, and -¡ Highest. Of these the first has but just now been-dealt with by Parliament, and I am sure the Bill passed daring the but session, through the exertions of Mr. Foreter will not lock the hearty good wishes of the whole population for its success. Time, and time alone, will prove its worth. The last of these three kind* will scarcely claim oar attention at the present time; so it ¿a Secondary education, the education of the mechanical and middle classes, the stay and backbone of England, that attracts our notice. What can be »aid for it? Little that is good. Certainly here and there, good schools ander able conductors have sprung up, but they are the exception not the rule. The majority of these schools are under the direction of speculators, men incapable to doing the work required, caring nothing whether that work be done or not, so that they live comfortably and are never required to exert themselves. I am writing this from a town containing some two score., of so-called middleclass schools, and of these 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 euch facts as 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 Mies A, B, and C, $o
and-шо } It would be a good thing for them to go homo and say, 'I am doing such and such lessons at school.' It would bo mentioned to friends, the prestige of the school would be raised, and an increase of pupils would be the ultimate result." Thus the useful was to give
way to the worthless ; but 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 the end of the term.
I constantly read in the correspondence columns of onr English Mechanic, that English houses cannot turn out certain work to equal that of Continental labourers. There must be a reason for this, and may it not be assigned to the lock of scientific training? The eye has not been trained by the inspection of beantiful 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 mach 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, &c., Äc., can all be overcome. It was but last year that many pounds were spent npon a machine in this town for the above object; the originators knew they could do it, but they haven't, nor w»uld they listen to advice. Again, but lately, another idea concerning "perpetual motion," was mooted and worked out in the brains of two workmen, and they would, but for your humble 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 useloss. 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 shall be compelled to obtain before entering npon his scholastic career. A plan has lately been mooted which meets with approbation from men celebrated for their knowledge 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 he 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 earning out these objects. A few of the aims would be as follows :—
1. The institution of normal colleges for the training of gentlemen who wish to enter the scholastic profession.
2. To recognise some examination, diploma, Ac, as sufficient guarantee 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 be overestimated.
8. The necessity of Government or other central supervision and examination of every school. At tho present moment the standard of a school is calculated by nothing. ... It is impossible to deeide upon the general tone of a school by the examination of a few of the best boys. (In inauy schools a/ею of the best boys are regiiLvly sent to tho Oxford or Cambridge middle-cla«s, and other similar examinations. The
public do not know the percentage of the school so sent).
4. The institution of a elub-hon?.o in London where appointments could be made, butines» transacted, Ac, and some means attached to it by which the incuba* «f agents could be avoided. (I ne'wl scarcely stau thu: the agente prey npon the -weaker vessel. The poo? assistant pays all, and the ail is no laughing matter whibt the *¿ah principal gets off ecot-free. Axe not both benefited to the same extent, so that both sho nli bear ihe fin* if it be fonnd needful to exact one ? >
5. Periodical meetings, At."
Such, then, is a rough draft of A scheme mo*rti by the editor of the Quarterly Jomrmal of Edmsattvwho has already issned invitations to a few rvprt *en.Uti»e gentlemen for a preliminary private mectnr to be held immediately, when f atare operation-« will W decided npon. Till now a mass of ill-armed audi»c pliuexl men, mingled with stalwart warriors, with ft* leaders cañante of onaecetanding the *itnation, к*. been fmitle—ly contending against the serried r»x. of ignorance. Is this to continuo? U too glacis t^-, wide and exposed, the rampart* too strong, not to Ы] before tee combined efforts of the reforming army? 1 do not for я moment believe that the endeavours of the^ noble men will bo fruitless, but suspect that they will prove conquerors. Mon, be up and doing, assist in the tight; the task is difficult; but, with England at it. wheel, who dare stand in the road? С H. W. В.
COMPOSITION OF THE METEORITES.
 Sir,—Can yon. or any of your astronomía readers, tell me if it is correct that organic matter inu boen found in meteorites? The meteDrites of Orgeai: contain, it is said, G per cent, of organic matter, ana M. Wühler inferred from this that wherever the meteorites came from organic matter and organisas must have existed. The organic matter is descrió,-: as a kind of block mould of carbon, oxygen, and hs drogen, in the same proportions as they occur in peat and is it possible that this subetanoe (which existed ir the meteorites along with the usual inorganic constituents) could have originally come from the вате placeas the meteorites themselves, or id it a foreign substance entirely?
If any of your astronomical correspondents coalJ give me some information on the origin oí these meteorites, I should feel much obliged to them; and can any reason be given why the meteoric iron and. »tones are so rich in nickel and iron, and comparatively poor in oxygen? Many geoVtgLstaaiiA physicists (I believe among them Professors В rayley and Newton J suppose the earth to have been formed by the aggregation of meteorites; bat from whence is this matte originally derived? and what is its present condition?
P. S.—Is it likely that meteorites, instead of being the remnants of former worlds, are the materials out of which worlds are forming? and how doe* this bear on the nebular theory of Laplace?
[31ß] Sib.—I am inclined to agree with the remarks of "V.R.C.S. a New Sab. " 45.70, for I think *'Sigma" might have been a little mere explicit^in hi« explanation of the sulphato of lead and manganese batteries. I have had a six-cell battery in constant use for fourteen months for domestic purposes, and during the whole of that time I have had no trouble whatever; they only requiring water to compensate for evaporation, and I can assure "M.R.C.9." that, practically speaking, they are as powerful now as wlien first charged. They are made as follows :—Get a quart jar glazed inside, in which fit a cylinder of zinc about iin. t hick ; next get a porous cell that will fit easily into the cylinders; now get some thin sheet-copper and mako four copper cups about 2in. diameter and solder these, ono above the other and about l£in. apart, on to a copper rod ¿in diameter, this will be the copper pole, Now mix sulphate of lead with water to the gnosisU-nce of clay, and fill the copper cups with it, place them in the porous cell and fill with water, charge the outer cell with sea-salt and water and it is ready for ose. I examined mine the other day and found but very liiilc wear in the zinc, in the copper the loss wa3 nof perceptible. I am now trying the manganese battery, some of which I have had in use seven months, and so far I am very much pleased with their action. I will send a sketch to scale (if worth inserting) of the lead battery.
NORFOLK GEOLOGY.—At the recent meeting of the London Geological Society the Rev. John Gnnn read, a paper "On the Rotative Position of the Forest Bed of tho Chillest'ord Clay in Norfolk and Suffolk, ond on the real Position of the Fores-t Bed," in which he stated that both at East on Bavent and at Kesalngland the Forest Bed is to be seen forming part of the bench or of the foot of the cliff, and underlying tho Chillesford clay. He considered that the soil of the Forest Bed hod bees deposited in an estuary, and that, after its elevation, trees of which the stools are now visible along the coast, grew upon it, and the true forest bed was formed. After the submergence of this, first freshwater, then flavio-marine, and finally, marino deposits were formed upon it: and the aatrjor proposed to give the whole of these deposits tho шипе of tho *' Forest Bed Series." The author suggested, that the Forest Bed itself is represented inland by the stony bed which lies immediately upon the chalk aud between it and tho fluvio-marine and marine crag«, his theory being that the surface of tbn chalk, after supporting а forest bod fauna, was gradually covered up by sueeee^ive crag deposits.
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."—
[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
[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
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 small quantities until the density reaches 45J Twaddell, or thereabonts. Care must be taken when putting in the ash that it is kept continually stirred, so as to dissolve every particle of it, for unless this »s attended to some oí it will get into hard cakes, which it is difficult to dissolve. When this density is attained, the liquid is drawn off into the settler, where all the eediment soon falls to tho 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. Tho clarified liquor is now drawn from the settler by means of the tap at the bottom and conveyed to tho pan again. The fire 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., 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 tho surrounding brickwork. Iron rods must bo 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 mother-liquor, is siphoned off, and the crystals allowed to drain, alter 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 largo 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 ¿cwt. of crystals can be made for less than they can be bought from the manufacturers, calculating at the rate рог ton. If " S. C." will take particular notice of the quantity of soda ash he uses the first time to bring a 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 its crystallizing density, viz. 54°, let him take a small quantity iu a ladle or cup, and blow on it with his mouth, when, if it forms a scum on the surface he may concludo that it is boiled enough. I trust that I have given the information sufficiently clear to be understood by " В, C." if not let him ask again for what is deficient.—
[4532.]—TELESCOPIC, Etc.—In reply to "H. A. C," it cannot fairly be considered good work for an 8¿in. silvered glass reflecting telescope to render the satellites of Jupiter visible in sunshine. One of the satellites, the 8rd, has been seen with only Sin. aperture, 50 minutes before sunset, by Mr. C. Grover. I have very frequently observed the satellites before sunset with a 4j4n. O. ti., and have no doubt that the 3rd could bo seen throughout an entire day with 8in. of aperture. Let your correspondent turn his telescope on ■»' Andrómeda and if he sees the components fairly divided he may be sure that his telescope is a very excellent one.— Hesperus.
[4541.1—EMBROIDERING MACHINE. —The machine which I think will suit " A Braider " and recommend him to see is the " Excelsior," Whight 4 Maun, 143, Holbom-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 needle for a pivot. I have had one nine months and am quite satisfied with it. The work though quito strong unpicks readily.—O. E. R.
[4540.]—DIVISION PLATE.—" Wahsrof" evidently has not given much attention to this subject or he would not recommend such numbers as he does. For oxamplc, a mau who has a circle of 720 holes (who ever had ?) cannot possibly have any occasion for 360,144, or 120. The numbers 221 and 209 are the most absurd possible, as one is 11 times 19 and the other IS times 17, and you cannot obtain twice or three times any of those numbers, as they are all primes, so that you bave to pay for boring 430 holes, of which only 60 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.
[4540.] DIVISION PLATE.—I have a lathe by Holtzapffel and ono by Buck, the division plate on the former contains the following 860,192, 144, 120,112 and 06, 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 ur 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 Legg.
[4556.]—TELEGRAPHY.—In answer to " Mus," he is right in supposing that "A" in the diagram is to prevent the wire slippiug off the pole. It is termed а "wiro 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 (иго wires fastened to one insulator.—Terminal.
[4560.]—PAINTING CISTERN.—If your cistern is well scraped and dried, a light coat of red load paint ought to remain good for years.—Vivís Spehandcm.
[-1563.J— BRASS COIN—is a Nuremberg counter; observe the letters RECHP. "Kechenpfcnniug" or counter; those letters are always sufficient for classing a coin among the German counters. Tho present bears oven tho English word "Counter."—Bernardin.
[4568.]—COPPER AND BRASS COINS.—The first ono is a Roman coin of the Emperor Probus, who reigned from A.D. 276 to A.d. 282. It is of the sise called 8rd or small bronze. The obverse bears the crowned bust of the emperor to the right, circumscribed IMP. С PROBVS. P. F. AVG. (Imperator Oaius Probus Pius
Felix Augustus.) Reverse: a woman standing, holding a branch iu her right hand, and a spear in her left. Inscription : COMES AVG. (Comes Augusti.) Common, worth 9d. to la. The brass one is not a coin at all, but a common card counter, quite worthloss.—Henry W. Henfrey, M.N.S., Ac.
[4564.]—TWO SILVER COINS.—No. 1 is a denariue of the Roman family of Antestia. Obverse: the winged head of the Pallas to tho right ; X for the value in front; and C. ANTE8TI. behind (Caius Antestius). Reverse: Castor and Pollux on horseback to the right, with their lances in rest. A dog running below. In the exergue ROMA. Thiacoin is common, worth 2s. Coined about 40 years B.c. The second coin is ancient Greek, but the drawing is very Indistinct.—Henry W. Henfrey, M.N.3., 4c, &c.
[4578.] 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 quantity of wood naphtha, and again, the wood naphtha itself contains a greater or less amount of tarry matter, according to the purification which it haa undergone. The well-known empyreumatic odour of methylated alcohol is due to the presence of tar and other products of destructive distillation.—An Associate Of Royal School or Minbs.
[4577.] INDUCTION COIL.—The inductive effect of a magnet is greatest at its middle, hence, as "Inductorium" stated, that of the coil is so because it depends upon the magnetism of the coro. Tho partitions do not waste the power as "Operator" «opposes, because they are notoíWiríon* butiuoííifiíioa*. They are sectional or vertical insulators m placo of the ordinary horizontal ones. I consider good paper soaked in paraffine better than gutta-percha tissue of the samo 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 asked for, though I nave mude many of the coils as fitted for medical use, snd have described them. I only make instruments for my own experiments, and induction coils are somewhat serious affairs, and have not, as yet taken up much of my attention.—Sigua.
[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 tho .quality of coal; tho perfect state of rcpair of all tho works ; to decide upon the degree of heat and duration of carbonisation, 4c, all of which can only be acquired by experience based on knowledge. This latter should bo 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'e is the best, Bowditch's are usefnl, and Hughes is a hash-up of a compilation published in Wealos' series : I do not remember the titles, and have no list at hand.—Sigua.
[4582.]—GOLD LEAF.—Gold books arc rubbed with red chalk, or crocus powder, I believe, bat it is done to prevent the gold leaf adhering to tho paper, and not, as "Chemicus " 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 pioce of thin boech, 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.
[4589.]—TENDER FEET.—I think J. T. Hill will find relief if ho turns his stockings inside out, and rubs them well with a piece of soap m listened in water. Boots with thick soles are not so »pi to blister tho feet as tliin ones. Blbleis also sumetimes arise from boots being much too large. Tightboots 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 tho purification which gas now undergoes there Is still too much sulphur in it, and 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 triff try seed, let him get ColUnxia bicolor, Lupinua nanus, Eijsiтиш Peroffiktanum, Ncuiophila intignU, 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, uot 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 soeu flourishing in London windows. Sunshine is not a necessity, but they should have as much light as possible. The creeping jenny does well to hang down in frout and hide the boxes. Above all things give the plants good wholesome mould, such as turfs cut from a meadow, 2in. thick, aud crumbled up with a little sand if necessary. Always keep the leaves clean by syringing or watering, as they act as lungs, and town so -it and dust soon block up their pores, and so" choke " the plants.—Saul Ryuea.
[4592.]—CHANGE WHEELS.-I think "С. С" had better beg, buy, or borrow Binns' second course, and read therein the chapters on wheel teeth. The scriber for striking the epicycloids is always a portion of a circle of one half the diameter of the smallest wheel of the set, which Willis puts at twelve teeth, and Binns proposes to make fourtceu the universal standard for, as it makes u better shaped tooth, the wheels will then iuterchango anyhow. If the wheel is 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 arc commonly only half the size of those used iu other machinery, the result is mnch the same tooth for the wheels in either case. Whore a wheel is always driven it requires no top to the teeth, which may all be turned off down nearly to the pitch line, and consequently the
teeth of the wheel which always drives do not require cutting much below tho pitch line, in fact only enough to clear the shortened teeth of tho other wheeL Ido not quite understand what " С. С. " means by the middle line of his query, as I never know of any particular rule for the case he proposes, beyond what I nave given above. —J. K. P.
[4597.]—INDIAN COIN.—It was struck by Tippoo Saib, the Sultan of Mysore, about the year 1790. It will be remembered that Tippoo was slain at the siege of Seringapatain on the 4th of May, 1799. He struck many copper coins from the Mohammedan year 1215 to 12Я7 (a.d. 1799). These coins were the double priiah; prinah, or pice, also called duda or sahrah ,- the baa pfitah, and the quarter p^isaA. All these coins are remarkably distinguished by the figure of the elephant upon them. If " J. N. D. C." would like to torward me his coin, I could toll him its exact date and value.—Henry W. Henfrey, M.N.S., 4c, 4c-, Markham House, Brighton.
(4599.]—EFFECTS OF CARBONIC ACID—Air containing more than 15 per cent, of carbonic acid is fatal to animal life; in its natural state it contains one part of carbonic acid in 2,500 parts (by measure), a larger proportion than this octs upon the nervous system as a narcotic poison.—T. W. Boord.
[4599.]—EFFECTS OF CARBONIC ACID.—If the proportion of carbonic acid is greater than 3 or 4 per cent, it acts as a poison,—Oxoniensis.
[4599.]—EFFECTS OF CARBONIC ACID,—According to Professor Huxley, the direct poisonous effects at carbonic acid have been greatly exaggerated, for it has been found that air containing from 15 to 20 per cest. of this gas may be breathed without producing any immediate evil effect, providing the quantity of oxygea in the air be increased in a like proportion. These experiments go to show that the destructive power sf carbonic acid depends more on the fact that its presen*) in air renders the proportion of oxygen too small, auf thus a species of suffocation or asphyxia is produce* togethor with any poisonous effects the gas may have. 1 the air were confined, as in badly ventilated rooms, taf carbonic acid would continue to increase ami the oxygen to diminish as long as the individual remained, and when 10 per cent, of carbonic acid is thus added to the air with the corresponding removal of oxygen asphyxia will take pluce. When a mnch smaller proportion of
Eure air, say 4 per cent., is replaced by carbonic acid, endliche and languiduess aro produced, and these often end in fainting.—Exhibitioneh At Koyai Congos Of Science.
[46O0.] PRINTING IN GOLD OR BRONZE.—Use gold-size instead of the ordinary ink. and apply gold-leaf or bronse powder when the ¡dieis sufficiently dry. Th« size, 4c, may be obtained ready tor usa at any prinlijig. material warehouse, as, for example, at F. turner'», Old Bailey, Е.С.—T. W. Booed.
—PRINTING IN GOLD OR BRONZE.—This may be easily and cleanly performed by rolling the type with gold size instead of the ordinary printing ink. Alter tho impression is " pulled," gold, silver, or bronze powder is dusted over the paper, aud tho whole wiped with a piece of cotton wool. Common printing ink answers just as well; but in this case, in wiping off the superfluous metal, care must be taken not to smear the letters, as the block ink would, of course, show on tho paper. Any colour niav be printed in the same manner; and particularly those which lose their lustre when mixed with varnish. Thus, ordinary red ink is "brought out" much better when it fa dusted with vermilion powder afterwards. — Sacl Rtxea.
Г460О7— PRINTING IN GOLD.—'• Amateur Typo" should moisten his type with size, or some glutinous [-.imposition, then print, and while the card is quite damp dust it with gold or bronze; when quite dry, «rctally brush off the superfluous metal with cotton wool.—Ab Initio.
Г46001— PRIXTING IN GOLD OR BRONZE.— "iuiHtcur Typo" should use gold size in place of ordinary printing ink, and во soon as the impression is taken dust the work over with bronze—procurable from any artist's colourman-sfterwardsveryUghtly Çle*nln£ the surface with a pad of cotton wool. He will find goUi far too expensive, whilst bronze will answer every purpose. The operation should bo performed m a warm room.—H. T. R.
Г46011-GILDING BOOK EDGES.—" A. H. D." should proceed in this fashion :—After the edges have been cut, wash with a mixture of one part candy sugar to four of Armenian bole, ground thoroughly together. Add tho white of an egg and some water. The wnoM must now be thoroughly beaten together, till sufficiently thin to be applied with а ЬгпиЬ. Use a came I-bur brush to applv the fluid, and when nearly dry, burais^ ,.„u, „ „nt rio andaniilv the gold-leaf on a pieo a
th a wot rag and apply tho gold-leaf on a P»ff' cotton wool. Some binders apply gum water »Haw laving on the mixture of bole and sugar; others away pa'intthe edges with a solution of isinglass ш «pmts, aud lay on the gold-leaf when nenrly dry.—Sobras.
 GILDING BOOK EDGES.—Sere» the book up n« tightly as possible between boards placed, e-voii with the edges, scrape the edges perfectly smooth with a steel scrapor, burnish with an agate, then colour oje r with red bole, or chalk ground in soap, rub immediate., у dry with flno clean paper shavings and burni-h again. The size, prepared by well beating up the white of an egg with three times the quantity of water, must then be applied evenly with a large caniel's-hair pencil, and the gold laid on with a tip. W'hcn dry burnish earetallj to avoid rubbing off the gold.—T. W. Boord.
Í4G01]— GILDING BOOK EDGES.-" A. H. D.~ should gild his edges as soon as cut, and if he wishes lit edges to show red under the gold, he should first colour the edges with vermilion mixed with glaire, and a 1 «LU Uoiwr ommoniir; when.dry moisten the edge with a littl» gold size, and while tho edge is damp lay on tho geU iseo reply to 4582). When thoroughly dry bumiah vrtth s bloodstone burnisher.—Ab Initio.
[4602.]— MELTING GLUE—Breakup your cake« of rin» into a saucepan or molting pot, and cover with wwler. Let it stand a fow hours to sonk; place it on the flrv ontll dissolved; bring it to boiling point, and «train It through a cloth, and it is completed. It found too Unci for your use add a little water; if too thin, place it Od the fire, the water will sooa evaporate.—CabinetMaker.
[4603.] MELTING GLUE.—Soak a cake of glue from 13 to 24 hoars in cold water, then drAln off the water, put it (the glue) in the glue pot, fill the outer vessel with boiling water and npply heat. The glue will speedily run into a liquid tit for use. The longer it is soaked tho more liquid it will be. Glue improves in quality by frequent melting.—J. W. Boord.
[4603.]—FISHING.—" Mr. Jamieson '* will find plenty of bleak and gudgeon in tho Lea, cither at Rye House, Tottenham, or Temple Mills; but he must romember that gudgeon iw i i.i near the bottom and bleak near the surface. Л good method of angling for bleak is to have a light fly-rod and line, and a No. 1 hook mounted on a bit of the very finest gut, stained greyish green. About lj or 9ft. from tho 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 havo ready some bran, mixed with sufllcient water to cause it to adhere on pressure and yet to crumble up readily when thrown into the water. Choose a likely spot for a swim, which ia easily discovered by tho 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 the best method, but bleak can bo taken with anything, only you must fish on the top. They are found in most streams producing dace and roach; and gudgeon aro to bo caught in nearly every runni tuj river in 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 largo stones, and net or spear the in. Thamos fishermen always rake the bottom when fishing for gudgeun; this is as good as ground bait, or better.—А. T., Staines.
[4604.]—PICRIC ACID is formed by the action of fuming nitric aoid npon many organic substances containing nitrogen, such as silk, indigo, salicln, &c, &c, but more cheaply by treating carbolic acid and its derivatives with nitric acid. It is a bright, yellow crystalline substance, possessing great tinctorial properties. It dissolves in about 90 parts of cold water, to which it imparte a yellow colour, and a bitter taste; it is on account 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 alo under trial for a short time, when, if there be any appreciable amount of picric acid present, the silk will bo 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 filiado.—An Associate Of The Royal School Of Miras.
[4604.]—PICRIC ACID.-Picric acid or tri-mtrophenic aoid, one of the coal-tar dyes, of cauary-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 sufllcient 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 partako of it. It may be easily detected as follows :—Take a smal test tube, say 4in. by |in., half fill this with the liquid to bo tested; add a small bit of putash or soda, about the size of a grain of wheat; warm this over a gaslight until dissolved; now add a small crystal of greeu copperas ; hold tho teat tube up to the light, and watch tho chango 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 tho action of nitric acid on indigo. Brilliant yellow scales, very bitter and highly poisonous; used in dyeing yellow, ita salts are mostly explosive with boat. It throws down a yellow crystalli je precipitato, soluble in water, with caustic potash.—J. W. Boord.
[4606.]—PROPELLING A VESSEL BY A WINDMILL. —A vessel could not be propelled íuad to wind by a windmill, for even supposing friction to be put out of the question, and the whole ol the power exercised by the wind on the windmill to bo utilized by the ecrew, 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 the 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.]—ORGAN BUILDING.—To make stop diapason speak louder. This can bo done—providing the scale will admit—by '* cutting-up" tho mouths of the pipes higher, as well as by taking out the plugs, which are sometimes put by tho bnilders into the feet to soften the tone by reducing the supply of wind. This requires considerable experience todo; and unless "W. Purlers" isa flrst class hand at voicing I should recommend Sbiv1яке his BtoP *° a r°8ulftr organ-builder, who will, if the thing is practicable, very soon do what he requires, whereas his own efforts may only render his stop uneven and perfectly unbearable. As regards hardening brass wire for pKllet-sprintîs, don't have an inch of it in an organ at all, unless you wish to have a constaut source ol annoyance in the ehapo of repairs. Steel and nal vanizejl iron wiro are almost universally used by builders for pallet-springs.—H. T. R.
-POLISHING VULCANITE.-''G. N. L." can
get a perfect surface on his vulcanite by romoving the scratches with a smooth waterayr stone (wet), and thou giving it a good pumicing at his lathe with fino pumice nndHttffbru-h. After washing the pumico oft* he can polish it with whiting and soft brush. He must keep turning his work about in different directions, so us not to keep brushing in one direction, for if he does, he will never get л surface.—J. O. P.
[4614 ]-ELECTROLYSIS.-This can be easily eilected by an electro-magnetic apparatus, if arranged to givoa1'quantity" current, and in one direction only, iüo ordinary instruments sold would be totally useless
as they are arranged to give a current of high tension or shocks, Instead of quantity.—Sigua.
— MANAGEMENT OF BEES.—The beet beefeeder is a wide-mouthed glass bottle holding about 11 pints. Half fill with syrnp and tie a piece of coarse cloth tightly over the mouth, place a piece of wire gause 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 the gauze. Last winter my bees consnmod about a pint in ten days, as nearly as I recollect, but they had very little stock honey in their hive. The bottle, complete, maybe had at Neighbour's, Regent-streot.—J. W. Boord.
[4631.]—CHLORIDE OF GOLD.—Dissolve the gold cuttings, which should not be toolarge, 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 readieet way to get rid of this is to ignite it and re-dissolve the metallic gold thus obtained in some more aqua regia, and proceed as before. —an Associate Of The Royal School Of Mikes.
[4621.]—CHLORIDE OF GOLD.—Dissolve the gold in aqua regia and evaporato to dryness over a water bath. The residue may then be dissolved in water.— Exhibitioner At Royal Colleoe Of Science.
[4621 &4C22.] CHLORIDE OF GOLD AND NITRATE OF SILVER.—Chloride of gold, or more properly ter* chloride 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 cryetaUlzo. To utilize your old solution of silver add a solution of common salt in excess, i.e., until no further precipitate is produced; collect tho 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 ceases 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, aud 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 bo re-crystallized twice to insure purity. Cuttings of papor filters, Ac, containing silver should be burnt, the ashes treated with nitric acid, and tho resulting liquid as above.—J. W. Boord.
[4622.]—NITRATE OF SILVER.—Do as you say. Evapornte down to dryness; powder It, and mix with some carbonate of noda, as a flux, and a little charcoal powder, and then fuse.—An Associate Of The Royal School Of Mines.
[4627.] — DISCOLORATION OF LEATHER. — In the process of tanning, leather is mad о to take up taunic and gallic acids ; these combine with iron, derived from the metallic surfaces of the press, and form tannate principally, and somo gállate of Iron, both of them are black, honco the stained leather; in fact black ink is formed. This discoloration may be prevented by not allowing the iron surfaces to enme 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 the 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 wero perfectly dry this would not take place. Brass moulds would not bo open to the same objection. —J. W. Boord.
[4627.J — DISCOLORATION OF LEATHER. — 11 G. A. G."is certain to get his leather discoloured while houses iron upon damp leather. Cannot he use boxwood or something similar ?—Ab Initio.
[4631.]—LATHE.—TO H. WILLIAMS.—I should say No. 12 gaugc-wheols 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 closo to where the thread terminates on the left of the gap. Of course the smaller the diameter of aorew 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 tako this opportunity of stating my 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 be, perhaps, 'difficult to get cut, and still more to get a nut made for it; and is moreover so at variance with usual practice, that I should not advise you to act on mv opinion, however firm it maybe, as I have not tried such a screw yot—though I have everything nearly ready for doing so. You might safely have one of ¿in. pitch, with a 4in. threaded screw, cut with a No. 8 eorew-tool. 1 advocate tho plan of making tho screw in two parts, viz., the plain part at the left-hand of the lathe terminating in a socket, into which either end of the screw may be keyed, a portion of the thread, say an inch at »■ach end, being turned away for the purpose. Close behind tho socket comes the extra bearing I propose ibovo, and then you may safely reduce the diameter of /our screw. I should strongly advise you to send your -terew to Wilkinson, No. 42, St. George's-road, London, to be cut, аз you will then have it of a true number of ithreads to on inch, which is commonly not the case in lithe screws.—J. К. P:
[4658.]—SILK WINDING.—Tho cocoons must bewail iteeptd in a warm soap-lye, and the floss taken iffuu';i he fibre will run easily: then five or six of the fibres are ,iken together, passed through a small eyelet, or guide, Lnd wound upon a largo reel. As soon аз any cocoon peoomes exhausted or runs down to a mere skin, it must о roplaced by a fresh one so as to keep the reeled '.bread uniform in thickness.—Crow Trees.
Г4640.]—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, price 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 oherry-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 tho hand-hammer to the proper thickness it i i of equal width throughout, as hammering the edge now will cause the corners to fly. After cutting square, and flatting the point, thrust the bill through the Are and heat well up before attempting to heat the end, turning it round so as not tu burn the edges; draw the point into.thc fire and heat to a brightish red, being careful of the corners. Harden by plunging about 2in. of tho point perpendicularly into a pailful of cold spring-water. If " R. IV 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.—"R. D." should use yellow
Erussiate of potash, and plunge Into urine, while red ot. As far as my experience goes, that never fail* iithe metal be good.—Ab Initio.
[4615.]—HYDROGEN LAMP.—I have a hydrogen lamp which is minus the platinum. I went to Jackson & Townson's.and asked for a bit of spongy platinum, and was told that it was a powder. The recoptaole for it is like a small 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 persons could see It at one time? or if by any means the current of electricity can be made more powerful t Would a coil of wire or helix add to the strength? The answer of some reader will oblige.—Enquirer.
[4647.]—PHOTOGRAPHIC—TO "MÜS," OR •' OPERATOR."—Will either of the above gentlemen kindly assist mo in the following matters ?—1st. By mistake I mixed the nitrato of silver in fiUeredioft water. Does it matter? If it does, what had I better do? 2nd. In looking on the focus screen, the figures (houses, pigeonhouse, saw-mills) are not only upside down, but reversed ( saw-mills on ff/i hand, Ac.). I don't think the latter position can bo correct. If it is not, how ehall I alter it' 3rd. I can get no image on the plate when the developer is poured on. What is tho remedy for this? I have taken the Enolish Mechanic regularly for several months, but as I do not see any information applying to my case, I have acted on " Mus'e "advice to another correspondent and beg leave to ask for it.—Mendicus.
[4648.]—TWO COINS.—If any reader of the English Mechanic would inform me through the medium of your pages the value and other particulars of the two
coins in my collection of which the above are sketches, they would greatly oblige.—Constahs Lector.
[4649.]— FRICTIOXAL ELECTRICITY.—I havo л cylinder electrical machine, the cylinder (length lHin., diameter 8in.) being supported on two brass pillars screwed into a brass ta bio, into which is also screwed the brass spring to which the rubber ie attached: and would esteem it a favour if any reader would kiudly explain why I can only get a lin. spark from the prime conductor (which is mounted upon a soparate glass)? —patty.
[46ГА]—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.
[4651.]—POWER OF WATER-WHEEL.—I shall feel thankful if any of my fellow-readers will kindly assist me with a plain rule to find the ho rse-power of an overshot water-wheel, diameter 16ft., breadth 4ft. Also, would a penstock of 8ft. or 10ft. above the wheel increase its power and also its velocity? If so, in what ratio ?— Miller.
[4652.]—TONING BATH.—lam often troubled with my toning bith not working welL Would any of your readers oblige mo with a good, trustworthy formula, givinggood uniform tono? £ think " Mus." " Operator," and others can supply mo with sound information.— John Terras.
r4$58,]—SUNDIALS.—One ol our friends, "E. L.G. , says sundials can bo easily made to show clock time throughout the year, by having two gnomons usod 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.— Sündiai«
[4654.] — OCCULTATION OF SATURN. — Will "F.r.a1s.," Mr. R. A. Proctor, or some other correspondent, kindly «plain the following?—It is stated in the Nautical Almanac that the planet Saturn is occulted bv the moon on the evening of the 30th September. The disappearance is predicted to occur at 6h. 4in., and the re-appearance at 7h. 18m. So far this is perfectly clear, but on referring to the " Elements of Occultation," in the same volume, I find that tho planet will be in conjunction with the moon at 6h. 13m. 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 6h. 12m. the planet will be actually occulted by the moon ?—Hespsbob.
[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. I wish I could say that two cells I use for bell-ringing.had gone untouched for as long a period. The fact is thai in my сазе 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 tho battery, and surely if It will go in one caso months without any attention! it will in another. Perhaps Mr. Stone will tiivenie ahint or two on the eubject,especially as to some less rough processor cleaning the connections, which at the rate I file them will soon be worn out—E. H.B.
 —GOLD COIN.—Will Mr. Henfrey or some numismatic friend kindly inform what the gold coin is.
and the value, of which I send the exact eise and copy? Plain on one aide. Weight 2 dwt. 23 gm—Hsvby Hoad.
[4657.] — KNOT-STITCH SEWING-MACHINE.— Would " Practical Hand,'' or some other brother reader, kindly answer the following? I want to make a knottedstitch sewing-machine, but do not quite understand how to make the looper, nor vet the length of stroke the needle should travel.—J. S. S.
[4658.]—CLEANING GILT FRAMES.—I should be glad to know the best way to clean the gilt frame of a chimney glass. As it is not of recent (cheap) manufacture, I think the gilt will bear operating upon. The gilt is not damaged by accident, but is of a smoky appearance, and being highly ornamental will cost too much toregild.—W. E.M.
[4659.1—TURNING HARMONIUM INTO AN AMERICAN ORGAN.—Could Mr. E. H. Jones (who wrote relating to American organs) toll 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, suchas the prongs of forks, Ac ?—J. W,
[4661.]—CATERPILLAR.—Will some reader of the English Mechanic inform me what is the name of this caterpillar? 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.
[4662.]—COIL.—I have made an induction coil with 91b. No. 16 primary wire, and lib. No. 85 secondary wire, 9in. long. How much battery power can I nee with safety, and how much spark ought I to get without condenser? How long a spark can I expect from a single J pint bichromate battery ?—Touteter.
[4663.]—BRAKE PIECE.—Can any one favour me with a description of a brake piece that reverses the current of electricity suitable for a coil ?—Tometeh.
14664.]—PRESSURE OF WATER.—Can any reader of the Enolisii 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 other 8in. diameter for 8ft. of its length, the bottom 4ft., are tin diameter. Is there any difference at the bottom of the two pipes in pressure per square inch ?—Ho Lb Eck.
[4665.]—PROBLEM.—Would any reader give me a solution of the following problem, taken from the first B.A. Algebra papor, London University? a. "An express train which ought to travel at uniform speed, after being an hour in motion, was delayed half an hour by an accident ; after which it proceeded at three-fourths of its original rate of speed, and in consequence arrived at the end of its journey lh. 50m. behind time. Had the accident occurred (and the same delay and subsequent retardation taken place) after the train had been an hour and a half in motion, the train would have been lh. 40m. behind time. Find the length of the line. 3. Supposing the above question were varied in the latter part of it by yonr being informed that 'had the accident occurred when the train had gono half-way t it would have arrived lh. 20m behind time;' would that information have been inoerrect?" Would it have enabled you to determine tho length of the line."— Beverley.
[4666.] -LIQUID BONE MANURE.—I shall be obliged if some of our correspondents can tell me how to dissolve boues, so as to make a liquid bone manure which may be used without injury to plants ?—8. W.
[4667.]— CLEANING 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.—Needlegpn.
[4668.]—THE LATHE.—TO "J. K. P."—I am just going to have a VUu. oentrelathe, with back gear, overhead, 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 ont to a lathe-maker to be done, such as the leading screw, &c, &c. I have enquired of a great many lathe-makers the price of such a lathe (first-class work, and all tho borings hardened steel), and find that some, euch as Evans, say about £100, and others gradually lower in price down to £25, which is the lowest estimate I can get. A man in Compton-street, 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 got such a lathe as I expect for that money. The mandrel will be iron, caee-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 care, asan amateur would use a lathe; besides I have not got £70 or £80 to lay out, and it would take mo years to savo so much, anil I want tho lathe with ав little delay as possible. If, on the other hand, I can get the casting*, and have them 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 good set of castings to work upon, and I think that as I could get through a great deal of the work myself, get the long leading screw cut by a lathe-maker, also the slide-rest screws, and havo the pulley divided, &c, Ac. (I could fit them in their places myself), it would reduce the cost very considerably—as ray time is my own, and, therefore, should not be reckoned in the expense. I have a very good 6in. lathe, 3ft. 6in. bed, with slide-rest, face-plate, and chucks, and I 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 describe in this letter, or, at least, the greater part of it? Will "J. K. P." kindly say what I had better do undor these circumstances?—Tometer.
[4669.]— OXYHYDROGEN MICROSCOPE.—CanIuse my achromatic microscope lenses (lin. and 2in.) with an oxyhydrogen lantern, SJin. condenser, for showing microscopic objects on a screen? A description of the mounting required would oblige, if possible.—E. H. Jones.
[4670.]—SATURN.—Will any subscriber kindly inform me what part of the heavens to look to to find Saturn, and the game for Jupiter, about from eight till ten in the night? Please to name the constellations they will be in about the 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 Am Ate и в.
[See "Astronomical Notes," by "F.R.A.S.," in this number.]
[4071.]—ICEBERGS.—Can you or any of your readers say why icebergs were met this year (1870) on tho banks of Newfoundland in March? They must have left 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 neoessary, 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 beueath, and the inclination being rigid? A speedy reply will much oblige. -W.J.
[4078.]—INDIAN COIN.—1 shall be much obliged if
any kind reader will describe the Indian ooppercoin, of which I forward sketch.—Collector.
[4674.]—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. 6, samo problem, an angle being substituted for the circle.—X. Y.
[4675.] -POND FOR GOLD-FISH.—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.—Vivís Spebanddh.
[46760 —NITRATE OF 8ILVER,—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-dis^olve it, so as to be perfectly neutral and fit for either bath or exciting paper ?—Paddy.
[4677.]— WATER POWER.—Would any brother reader inform me what power I could get from a fall of water fifteen feet through an inch pipe, if applied to a turbine wheel? And wliat size, &c, of u turbine would do? Abo what kind of a turbine would be best?—A Reodlae Subscriber.
[4G78.]—BOURNE ON THE STEAM ENGINE.—I am about to purchase a work on the steam engine. Is there a bettor work on the subject than Bourne's? If there is would one of your readers tell me the price, publisher, &c. ?—Tiios. Watson.
[4679.1— CIVIL ENGINEERS* EXAMINATIONS.— Would »ото kind correspondent give me a little information about the Instituto of Ci\il Engineers? What is necessary to become a member? and what is re
quisite to become a C.E., the cost ot examination, &c.? —Terminal.
[46Ö0.1 —BLEACHING С ALIGO.—Perhaps some correspondent can give a few hints on the best way to bleich brown calico ?—N*.
[4681.]— INSULATION.—What is the least thiekn«* of solid ebonite to safely insulate the extremities ol a, secondary coil giving 4in. sparks in air? Also, what is the comparative resistance of gutta-percha and tbnew insulating material (Dr. Matthiessen'b) made bj Field à Co.? On writing to the manuiaetorersformfar mation on this point, they simply sent me a sample, which I find to be softer than the above named gum, 6olubloincbdoroform,&c.,audmeRingat I'1* (130 S "....contains paraffine. But.the above question I am unable to accurately determine. Also, what can I cover copper wires with to prevent them accumulating a deposit Ы gold when hanging articles in the gilding baths? Solution (cyanide) attacks gutta-percha. Answer next week, if possible, will greatly oblige.—O. K.
[4682.]—TONING BATH.—Will "Mus" be ao кЫ as to give me his formula for toning bath that gives i purple tint? I cannot find it in back numbers, аз I have only taken it a few months.—Phqtogbajpheb.
[4683.]—VALVE FACINGS OF CYLINDERS.—ОШ J. С Molton or any other obliging subscriber tell m* if the valve facings of model cylinders are east ou, er whether they are put or brazed on after it is turned ; asd If caet on how is the cylinder Onioned off? also, abouM I put anything in my crucible (brass) to make it mc free in casting, and how to avoid the scans or oxide frw going in with it, as it chokes up the moulds ; and do tit* moulds require to be heated? Thanks to# "J. С. M.4 fcr his last instruction on cylinders.—Лм Atïti: Bras* Founder.
[4684.]—TYPE.—Would any reader be kind enougbi; inform me whether there is any decisive test to extinguish "pirated" from genuine ** faces" in type ; mi whether, if in equal quality of metal the former h is serviceable to the printer?—Countbï Printer.
[4685.]—GILDING ELECTRO.—Will some practkielectrician give me some information upon what known to the trade as solid depositing—i,e., manuUt turing solid articles by depositing gold in the way that copper is deposited? Is the solution worked warm oi cold? What battery power is used, arranged tor quantity or intensity? What is the right proportion of the Areas exposed of the anode and the cathode? What is the best surface to deposit upon? 2 believe there taust be a large quantity of gold in the solution.—W. H. Corns.
[4666.]—INSULATION.-TO "INDUCTORIUM/*—I wish to ask "Inductoriuiu," who describes » mod« of making a coil on page 472. No. 17ô, il hü fmd3the> insulation between the primary and secondary coila sufficient? In coils of the ordinary construction, only a small part of the secondary circuit approaches tie primary, being the layer next to the reel. Inthe vertkul mode tue two extremities of the secondary coil are separated from the primary by only tho thickness of the reel, and from communicating with each other by tint« that thickness plus the resistance of the primary between the two points. In his case the terminale are insulated from each other by their silk covering Мм the thickness of the reel, and one of the rings plus the length of the primary with its cotton covering. This amounts to only Jin. solid ebonite, the rest of the resistance certainly being not equal to ¿in. of tho same. la lin. of ebonite enough insulation between the terminals of a. wire giving ffin. and 4in. sparks in air? For his sake, 1 certainly hope so.—W. H. Coffin.
[4697.]—"PANCREATINE" AND "PANCREATIC EMULSION."—The above preparations aro excellent remedies for indigestion, and are very useful for taking with cod-liver oil, but to buy them comes expensive. If any reader would inform me how I could prepare some I should feel greatly obliged.—H. H.
[4688.]-SEPARATING BEESWAX FROM RESIN, &c.—I should feel greatly obliged if any reader could inform me how to separate beeswax from resin and ne&Vs foot oil,with which it has been mixed?—Cab In кт-Макеи.
[4689.]—PEDOMETERS.—Would any brother reader give me a description of the actio» of the pedometer?— An Enquirer.
[4690.] —HOROLOGICAL.— Will seme of our fcorologieal friends who are adepts at the use of tho terms give me some practical infraction« how lam to proceed in turning down the collet of a verge for fixing oa tho balance? What kind of bow am I to use—its shapf, strength, and string—also what kind of graver mast I use; size of cutting angle it must have, position ttf the hand in using, length of stroke for the bow, quickness ot speed to suit best; aud, above all, whether it is tt¡*»i *• cut with the work revolving to the graver or ßtm the graver? I find in practice that I camnot uwiee виса progress when I attempt to cut the work revuiving with its upper surface towards the graver. All that I can do appears to be a mere »crape. But in the return *trok.e, when the under surface of the work revolves towards the graver I make hotter progress. In fact lhawe frequently taken hold enough to break the verge ia tw. Where is the fault, is it in the bow, the graver, or my eelf? My friends may judge for tliemaelves of my progress when 1 tell them that it will take ui- J\ h*u..i of hard cutting, scraping, and scratching to turn 4j • • the collet of a polished verge, previous to раШша o; the balance when an adept could do tho same work il half an hour. I also wish to know how the pivots ol tb pinions are got to the required size. Arc they turxst■■■■■■ í '¡ the graver or filed doum f I have frequently put iv new pinion-', but always Ule them down to the reqairvi size in the turas, by placing the end of the pinion in* notch at the cud of the centre of tho torus witb iL end of the rest as a guard, to keep the edge of the fib from running away from tho shoulder of the pivot. 1« it the proper way ?—Scrape.
[4691.]— POWER OF ENGINE.—Would "Vert menus " give me the power of an engine whose cylinder J*¿in. in the bore and of -tin. stroke, by the rule he maintains in your last week's issue (4471), and what will b? the necessary thickness of boiler pUte, aud pressure oi steam to work at to attain the power of une höre« ?— R.W.