and ammonia it is precipitated as a crimson powder; of course depends on the work it has to do. Third, the alkaline earths give purple precipitates." Green Smee's. Fourth, answered by the second. Lastly, yes.precipitate is obtained by mixing solutions of cupric R. M. sulphate (or nitrate) and sodic carbonate. I have often obtained this precipitate, but not recently, and I do not remember whether it is dark or light.-OXONIENSIS. [4224.]-TREATMENT OF A CHRYSALIS.-Pupe 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 fin., and on top of the earth there should be kept a rag moistened about once a week, just sufficient to prevent the earth becoming dry. Other kinds do not require any particular treatment.

INLET

INLEY

C.

7ST

FIC.I

T

FIG.2

OUTLET

B

OUTLET

he front taken off; Fig. 2 is a plan of the same at the ine A B; D D is the diaphragm, the face is of stout tin, And the sides of very supple leather; B is a bracket, onnected to same at the joints or hinges, H H; G is he guide rod, carrying the 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 or 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 ne lever and valve 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 tangent rod each revoluion, and prevents the meter being worked backwards by dishonest persons. The gas goes in at the pipe arked "inlet," and through the one shown by the dotted ine from A, and enters the valve box at the hole shown a Fig. 2. It then passes through the valves into the iaphragms or measuring chambers, back again hrough the valves, and along the other pipe, shown by lotted line to B. The inlet and outlet pipes are carried lown the sides of the meter below the dotted line, but hey only act as siphons to catch the condensation. The liaphragms move backwards and forwards like two pair f bellows, and as the outside is used as well as the inide, it thus makes four measuring chambers, which re filled and employed alternately by the action of the alves. The distance over which the diaphragms travel teach revolution is regulated by the tangent T being toved nearer to or farther from the centre spindle to which it is fixed. The valves have three holes or ports; sie 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 hole that is uncovered is open to the gas coming Com the inlet, and No. 2 is always open to the outlet ipe. Nos. 1 and 3 are connected with the inside and utside chambers, which are thus alternately connected vith inlet and outlet. There is a cover to the valve box, o that the gas does not get into the top of the meter, ind the crank spindle works in a stuffing-box, the same As the guide rods. 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, except by taking the top off and moving the tangent.JOHN H. RUMSEY.

[4159.]-PHOTOGRAPHY.-I would advise " "Young Photo" to give "Newman's Diamond Negative Varnish" trial, and I don't think he will give it up. It requires very little heat, dries a clear surface, and never gets acky. I have used it for some time, therefore speak from experience.-JOHN TERRAS.

[4200.]-PRECIPITATING COCHINEAL.-The following is taken from W. A. Miller's "Elements of Chemistry," Vol. III.:-" After treating the powdered insects with ether to remove the fat, the insoluble portion is digested with water, and precipitated as a purple lead lake by plumbic acetate. This must be well washed, decomposed by sulphuretted 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

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

[4490.]-WELDING CAST-STEEL.-Take 1oz. smelts blue, oz. rock salt, 2oz. borrocks, pounded together and fused in a ladle over the fire, and when cool reduce to powder; heat the steel to what smiths call a greasy heat; use the powder the same as sand. The weld will be much stronger if veed together instead 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 steeping in a weak logwood decoction for about five minutes, and rinsing afterwards in alum-water.-VIVIS SPERANDUM.

[4518.]-MYROBALANS are dried fruits of different sorts of Terminalia, myrobalan order or Combretacea, imported from India for the use of dyers and tanners.

[4242.]-INCRUSTATION IN BOILERS, ETC.-The following description of an invention for the prevention of incrustation in boilers, is extracted from the Student and Intellectual Observer, No. XIII. (February, 1869)."Among the many inventions for effecting this object, one by Mr. C. Weightman Harrison, of Clapham Junction, is simple, and 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 forms 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 he 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 precipi--BERNARDIN. tated matters. Sometimes he varies the method of carrying out his invention by means of an additional electrical source, so arranged as to transmit alternately positive and negative currents to the shell of the boiler, and to the 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 carbonate of lime insoluble, and capable, under certain circumstances, of still forming a scale.-S. . . . R.

[4270.]-CHEMICAL.-The following is taken from Fownes'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 the residue. This product, heated with sodium in a wrought-iron crucible, yields magnesium, which may be freed from impurities by distillation. Metallic sodium may be prepared in the laboratory by distilling in an iron retort 717 parts of dry sodic carbonate, 175 parts 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."OXONIENSIS.

[4274.]-CUPELLING.-The best and most 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 the 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 the 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 New 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 be weighed during each stage of the process.-M.R.C.S. (A New Subscriber).

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

[4520.]-PERCH FISHING.-The 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, with a stout top and running tackle, good red worms or big fish are never found in shallow water. Use a rod back under the back fin, in preference to the lip, as the (for large fish) minnows; hook the minnows through the perch seizes the bait crossways; by this method, the hook is at once in his mouth, and you can strike immediately. The "paternoster" is a very killing way to fish for perch, but I would not recommend an amateur to try it as it requires some considerable practice to get into the way of using it.-TERMINAL.

[4520.1-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 ruffle on the water assists the angler somewhat. For small perch a "general rod" will suffice; a common line with good-sized gut, and a No. 4 or 5 hook baited with lob worm, grub, or caterpillar; a paternoster line, armed with various baits, is useful for an unknown locality; and perch swim and feed at all depths. For large perch, a strong rod line and swivel trace, armed with minnow or gudgeon, is usually the most killing bait; spinning by tail and gorge hook is also successful, the latter especially in water where there are many weeds. Most canals or slowrunning streams afford perch fishing.-VIVIS SPERANDUM.

sieve.

[4521.]-EXTRACTING HONEY FROM THE COMB. -Cut the combs in a horizontal direction into small pieces and place them in a sieve over an earthen jar. Draining may take two or three 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 the honey so obtained will be inferior both in quality and colour, as a portion of bee-bread would be pressed through the honey of the finest quality, he must strain the combs If an "Amateur Bee-keeper" wishes to get from the outside of the hives by themselves, keeping centre of the hives are usually darker coloured, and the the first drainings separate, as the combs from 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 deal of very useful information on all points relating to bee-keeping in No. 3 of "Manuals for the Many,"-S. W.

[4861.]-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" Amateur Bee-keeper" desires; but he will find a great as a drinkable alcohol without the naphtha, but notwithstanding this, methylated spirit may undoubtedly be liking. As a rule all the tinctures now sold in chemists' drunk as such by any person who finds the flavour to his shops, are prepared with the methylated spirit, and many of such tinctures are for internal application. If "Shellac" desires, 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 twelve drops of diluted phosphoric acid, which has a tonic effect, and makes the oil agree better with the stomach. The 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 lung. To prevent the oil staining the linen a piece of oil silk with a bit of flannel next the skin will be required. My wife has tried the above for the last three months, and am thankful to say has derived much benefit.-H. K. N.

[4380.]-COLZA OIL is a general commercial name employed in France, Belgium, &c., for the oil manufactured by expression from the seeds of different species of Brassica, and has there the same signification as " rape oil" in England. "Colza," koolzaad, means cole or cabbage seed. "Colza" is the French name for " rape seed," says Mr. P. L. Simmonds, in his "Dictionary of Trade Products."-BERNARDIN.

[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 ever-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 Smee keeps in action longest: the length of time

[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 box and gland, 3 pipe from the engine, and 4 pipe from tried it myself. 1 is a ball-joint, 2 a common stuffing the boiler.-J. S. S.

[4581.]-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 requires, and if there are any in the vicinity in which he any of the alkali manufacturers in such quantities as 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 3in. 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 in to within 6in. of the top, and brought to a boiling heat, after which the ash must be thrown in in

small quantities until the density reaches 45° Twaddell, or thereabouts. 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 is attended to some of 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 sediment soon falls to the bottom. In large manufacturing establish ments 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 fire is urged, and the contents of the pan kept in a state of ebullition until the density reaches 54 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 case 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 mother-liquor, is siphoned off, 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 fewt. 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 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 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.

ones.

[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 The partitions do not upon the magnetism of the core. waste the power as "Operator" supposes, because they are not additions but substitutions. They are sectional or vertical insulators in place of the ordinary horizontal I consider good paper soaked in paraffine better As I than gutta-percha tissue of the same thickness. 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 have made many of the coils as fitted for medical use, and 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.-SIGMA.

teeth of the wheel which always drives do not reque cutting much below the pitch line, in fact only scien to clear the shortened teeth of the other wheel is not quite understand what C. C." means by the mida line of his query, as I never knew of any partedes for the case he proposes, beyond what I hate gian

-J. K. P.

[4597.]-INDIAN COIN.-It was strad E Saib, the Sultan of Mysore, about the york 2 be remembered that Tippoo was slain ty inga patam on the 4th of May, 1799. . . y copper coins from the Mohammedan (A.D. 1799). These coins were peisah, or pice, also called dudu la peisah, and the quarter peisah. are remarkably distinguished by elephant upon them. If "J. N. D. C. ward me his coin, I could tell him i value.-HENRY W. HENFREY, M.N.S.: Yorkham House, Brighton.

[4599.]-EFFECTS OF CARBONIC AL ag taining more than 15 per cent. of carbal to animal life; in its natural state it ea of carbonic acid in 2,500 parts (by measure? narcotie poison.-T. W. BOORD. portion than this acts upon the nervous

[4599.]-EFFECTS OF CARBONIC ACIDA. proportion of carbonic acid is greater than c cent. it acts as a poison.-OXONIENSIS,

[4599.]-EFFECTS OF CARBONIC ACTD.ing to Professor Huxley, the direct poisonous elej carbonic acid have been greatly exaggerated, tra been found that air containing from 15 to 20 pers. of this gas may be breathed without prodact immediate evil effect, providing the quantity of in the air be increased in a like proportion. The periments go to show that the destructive pose carbonic acid depends more on the fact that its prese in air renders the proportion of oxygen to smals thus a species of suffocation or asphyxis is prode together with any poisonous effects the gas may have.! carbonic acid would continue to increase and the oxyge the air were confined, as in badly ventilated rooms, 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 place. When a much smaller proportion of pure air, say 4 per cent., is replaced by carbonic acid, headache and languidness are prodaced, and these often end in fainting.-EXHIBITIONER AF ROYAL COLLEGE OF

SCIENCE.

[4579.] DUTIES OF GAS ENGINEER.-These are very extensive, and vary very much with the size of the In any case he has to keep up good discipline. works. 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, &c., all of which can only be acquired by experience based on knowledge. This latter should be a moderate acquaintance with chemistry, and [4600.] PRINTING IN GOLD OR BRONZE-Use the qualities of materials. In large works the ordinary knowledge of a civil engineer is needed, such as relates gold-size instead of the ordinary ins, and apply gold-leaf or bronze powder when the size is sufficiently dry. The to strength of materials and forms, as well as the principles of construction, and a good acquaintance with me- size, &c., may be obtained ready for use at any printing chanical drawing. There are many books upon the sub-material warehouse, as, for example, at F. Ullmer's, Old ject, of which perhaps Clegg's is the best, Bowditch's are Bailey, E.C.-T. W. BOORD. useful, and Hughes is a hash-up of a compilation published in Weales' series: I do not remember the titles, and have no list at hand.-SIGMA.

[4582.]-GOLD LEAF.-Gold books are rubbed with red chalk, or crocus powder, I believe, but it is done to prevent the gold leaf adhering to the 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 piece of thin beech, called a trindle, is rubbed on the workman's head, and then applied to lift the gold. 2nd. Srd. A gilder's tip. 4th. A A piece of stout paper. piece of cotton wool.-AB INITIO.

Boots

-W.

advice

[4590.]-TOWN GARDENING."A Factory Lad" will not succeed in growing geraniums and fuchsias any where 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, and plants of any kind exposed to its effects cannot thrive, and will scarcely live. If "A Factory Lad" will accept my 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 will try seed, let him get Collinsia bicolor, Lupinus nanus, Eysi mum Peroffskianum, Nemophila insignis, 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 necessity, 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, 2in. 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 soot and dust soon block up their pores, and so“ choke "the plants.-SAUL RYMEA.“ [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 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 Binus proposes to make fourteen the universal standard for, as it makes a better shaped tooth, the wheels will then interchange 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 are commonly only half the size of those used in other machinery, the result is much the same tooth for the wheels in either case. Where 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

[4600]-PRINTING IN GOLD OR BRONZE-TE may be easily and cleanly performed by rolling the ty with gold size instead of the ordinary printing in After the impression is "pulled," gold, silver, or bronne powder is dusted over the paper, and the whole wiped with a piece of cotton wool. Common printing ink answers just as well; but in this case, in wiping of the superfluous metal, care must be taken not to smear the letters, as the black ink would, of course, show on the paper. Any colour may be printed in the same manner and particularly those which lose their lustre mixed with

varnish. Thus, ordinary red in "brought out" much better when it is dusted vermilion powder afterwards.-SAUL RYMEA. [4600.]-PRINTING IN GOLD.-"Amateur T should moisten his type with size, or some glute composition, then print, and while the card is damp, dust it with gold or bronze; when quite dry. carefully brush off the superfluous metal with cothe wool.-AB INITIO.

[4600.]-PRINTING IN GOLD OR BRONZE"Amateur Typo" should use gold size in place of ord nary printing ink, and so soon as the impression taken dust the work over with bronze-procurable fr any artist's colourman-afterwards very lightly clean the surface with a pad of cotton wool. He will find far too expensive, whilst bronze will answer every pose. The operation should be performed in a

room.-H. T. R.

Use a c

[4601.]-GILDING BOOK EDGES.-" A. E. ? should proceed in this fashion:-After the edges h been cut, wash with a mixture of one part candy The to four of Armenian bole, ground thoroughly to Add the white of an egg and some water. must now be thoroughly beaten together, till sn thin to be applied with a brush. brush to apply the fluid, and when nearly dry, with a wet rag and apply the gold-leaf on n cotton wool. Some binders apply gum wate laying on the mixture of bole and sugar; othesney paint the edges with a solution of isinglass, and lay on the gold-leaf when nearly dry.-S

[4601.] GILDING BOOK EDGES.-Screw the hook with the edges, scrape the edges perfectly smooth wi up as tightly as possible between boards placed a steel scraper, burnish with an agate, then colour ove dry with fine clean paper shavings and burnish aga with red bole, or chalk ground in soap, rub immediste The size, prepared by well beating up the white of at egg with three times the quantity of water, mnst the be applied evenly with a large camel's-hair pencil, a the gold laid on with a tip. When dry burnish careially to avoid rubbing off the gold.-T. W. Boord. BOOK EDGES.-"A. H. D. [4601.]-GILDING should gild his edges as soon as cut, and if he wishes the edges to show red under the gold, he should first colou the edges with vermilion mixed with glaire, and a little liquor ammonia; when dry moisten the edge with a little gold size, and while the edge is damp lay on the gold (see reply to 4582). When thoroughly dry burnish with & bloodstone burnisher.-AB INITIO.

[4602.]-MELTING GLUE-Break up your cakes of glue into a saucepan or melting pot, and cover with water. Let it stand a few hours to soak; place it on the fire until dissolved; bring it to boiling point, and strain it through a cloth, and it is completed. If found too thick

for your use add a little water; if too thin, place it on the fire, the water will soon evaporate.-CABINET

MAKER.

[4602.] MELTING GLUE.-Soak a cake of glue from 12 to 24 hours in cold water, then 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 fit for use. The longer it is soaked the 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 the Lea, either at Rye House, Tottenham, or Temple Mills; but he must remember that gudgeon swim near the bottom and bleak near the surface. A 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 1 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 adhere on pressure and yet to crumble up readily when thrown into the water. Choose a likely spot for a swim, which is easily 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 the 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 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 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, &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 imparts 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 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

OF THE ROYAL SCHOOL OF MINES.

[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 300,000 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 tube, say 4in. by in., 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 test tube up to the 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 scales, very bitter and highly poisonous; used in dyeing yellow. its salts are mostly explosive with heat. It throws down a yellow crystalli e precipitate, soluble in water, with caustic potash.-J. W. BOORD.

as they are arranged to give a current of high tension or shocks, instead of quantity.-SIGMA.

[4640.]-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 Sd. or 4d.-CROW TREES.

[4618.]-MANAGEMENT OF BEES.-The best beefeeder is a wide-mouthed glass bottle holding about 1 pints. Half fill with syrup and tie a piece of coarse cloth tightly over the mouth, place a piece of wire [4841.]-MILL BILLS.-"R. D." can get his bills to gauze over one of the openings in the board form- stand if he is careful not to heat them beyond a bright ing the top of the hive, and turn the bottle quickly cherry-red when drawing down the points. The process upside down placing it at once on the gauze. Last win- requires skill, no chemical being used in the water. ter my bees consumed about a pint in ten days, as nearly Begin by carefully and regularly heating the point to as I recollect, but they had very little stock honey in be first drawn, and sledging it down to about one-half their hive. The bottle, complete, may be had at Neigh- more than the intended thickness, tapering it in width so that when drawn by the hand-hammer to the proper bour's, Regent-street.-J. W. BOORD. thickness it is of equal width throughout, as hammering [4621]-CHLORIDE OF GOLD.-Dissolve the gold the edge now will cause the corners to fly. After cutting cuttings, which should not be too large, in aqua regia, square, and flatting the point, thrust the bill through the this should contain more hydrochloric acid than fire and heat well up before attempting to heat the end, nitric; evaporate down on a water bath, when a red deli- turning it round so as not to burn the edges; draw the quescent mass of chloride of gold will remain. If a point into the fire and heat to a brightish red, being careful pale yellow powder be left on taking up with water do of the corners. not throw it away, for it is the sparingly soluble proto-point perpendicularly into a pailful of cold spring-water. Harden by plunging about 2in. of the chloride of gold. The readiest way to get rid of this is ff" R. D." accomplishes all this skilfully, being sparing to ignite it and re-dissolve the metallic gold thus obtained in some more aqua regia, and proceed as before. the hardest millstone.-T. A. of heat, though not of labour, his bills will stand dressing -AN ASSOCIATE OF THE ROYAL SCHOOL OF MINES.

[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 of 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 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.

[4621]-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 COLLEGE OF SCIENCE.

[4621 & 4622.] 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 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 contain ing 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, 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.

[4607.]-ORGAN BUILDING.-To make stop diapason speak louder. This can be done-providing the scale will admit-by "cutting-up" the mouths of the pipes higher, as well as by taking out the plugs, which are sometimes put by the builders into the feet to soften the tone by reducing the supply of wind. This requires considerable experience to do; and uxless "W. Por ters" is a first-class hand at voicing I should recommend him to take his stop to a regular 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 pallet-springs, don't have an inch of it in an organ at all, unless you wish to have a constant source of annoyance in the shape of repairs. Steel and gal vanized iron wire are almost universally used by builders for pallet-springs.-H. T. R.

[4611.]-POLISHING VULCANITE.-"G. N. L." can get a perfect surface on his vulcanite by removing the scratches with a smooth waterayr stone (wet), and then giving it a good pumicing at his lathe with fine pumice and stiff brush. 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 as not to keep brushing in one direction, for if he does, he will never get a surface.-J. C. P.

[4614.]-ELECTROLYSIS. - This can be easily effected by an electro-magnetic apparatus, if arranged to give a "quantity" current, and in one direction only. The ordinary instruments sold would be totally useless,

[4622.]-NITRATE OF SILVER.-Do as you say. Evaporate down to dryness; powder it, and mix with some carbonate 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 the process of tanning, leather is made to take up tannic and 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 allowing the iron surfaces to come in contact with the formed. This discoloration may be prevented by not 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 were perfectly dry this would not take place. Brass moulds would not be open to the same objection. -J. W. Boord.

[4641.]-MILL BILLS.-"R. D." should use yellow prussiate of potash, and plunge into urine, while red hot. As far as my experience goes, that never fails if the metal be good.-AB INITIO.

QUERIES.

[4645.]-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 receptacle 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?

[4631.]-LATHE.-TO H. WILLIAMS.-I should say 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 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 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. You might safely have one of in. pitch, with a 4in. threaded screw, cut with a No. 8 screw-tool. I advocate the plan of making the screw in two parts, viz., the plain part at the left-hand of the lathe termi nating in a socket, into which either end of the screw may be keyed, a portion of the thread, say an inch at Close each end, being turned away for the purpose. behind the socket comes the extra bearing I propose bove, and then you may safely reduce the diameter of your screw. I should strongly advise you to send your screw to Wilkinson, No. 42, St. George's-road, London, to be cut, as you will then have it of a true number of hreads to an inch, which is commonly not the case in the screws.-J. K. P.

[4638.)-SILK WINDING.-The cocoons must be well steeped in a warm soap-lye, and the floss taken off un'i the fibre will run easily: then five or six of the fibres are aken together, passed through a small eyelet, or guide, and wound upon a large reel. As soon as any cocoon becomes exhausted or runs down to a mere skin, it must e replaced by a fresh one so as to keep the reeled thread uniform in thickness.-CROW TREES.

F.R.M.S.

[4646.]-MAGNETO-ELECTRIC MACHINE.-Would some kind brother reader inform me if any experiments from their ordinary medical use,-if so, I should like to can be performed with one of these machines apart 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? Would a coil of wire or helix add to the strength? The answer of some reader will oblige.-ENQUIRER.

[4647.]-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 soft 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 left hand, &c.). I don't think the latter position can be correct. If it is not, how shall 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 respondent and beg leave to ask for it.-MENDICUS. my case, I have acted on "Mus's " advice to another cor

[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.-CONSTANS LECTOR.

[4649.]-FRICTIONAL ELECTRICITY.-I have a cylinder electrical machine, the cylinder (length 18in., diameter 8in.) being supported on two brass pillars screwed into a brass table, into which is also screwed the 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 fin. spark from the prime conductor (which is mounted upon a separate glass)?

-PATTY.

[4650.]-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.-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.

OCCULTATION

OF

SATURN. - Will

[4654.] "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 is occulted by the moon on the evening of the 30th September. The disappearance is predicted to occur at 6h. 4m., 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 the planet will be in conjunction with the moon at 6h. 12m. on the same date and that at the time of conjunction the planet will be this be, when at 6h. 12m. the planet will be actually occulted by the moon ?-HESPERUS.

situated 56m. of arc distant from our satellite. How can

[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 that 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, &c., until quite bright. This is the only trouble I have with the battery, and surely if it will go in one case months without any attention, it will in another. Perhaps Mr. Stone will give me a hint or two on the subject,especially as to some less rough process of cleaning the connections, which at the rate I file them will soon be worn out.-E. H. B. [4656].-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 size and copy? Plain on one side. Weight 2 dwt. 23 grs.-HENRY HOAD.

[4680.]—BLEACHING CALICO-Peny » spondent can give a few hints on the hard work and brown calico ?-N2.

of solid ebonite to safely insulate the mes [4681.]-INSULATION.-What is the las secondary coil giving 4in. sparks in the comparative resistance of gas new insulating material (Dr. M.S Field & Co.? On writing to the m which I find to be softer than the mation on this point, they simp soluble in chloroform, &c., and melta rank contains paraffine. But the above ga to accurately determine. Also, wha,& per wires with to prevent them accum est of gold when hanging articles in the lution (cyanide) attacks gutta-perca week, if possible, will greatly oblige.-[4682.]-TONING BATH.-Will ~ Ms as to give me his formula for toning parple tint? I cannot find it in back only taken it a few months.-PHOTOGRAFE

86

est

Loader" recommend fine emery-paper for cleaning gun-quisite to become a C.E., the cost of examine e barrels every time that they get foul? I should imagine -TERMINAL. that it would wear them much more than tow wrapped round the cleaning-rod would.-NEEDLEGUN. [4668.)-THE LATHE.-TO "J. K. P."-I am just going to have a 44in. centre lathe, 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 out to a lathe-maker to be done, such as the leading screw, &c., &c. I have enlathe (first-class work, and all the borings hardened quired of a great many lathe-makers the price of such a steel), and find that some, such 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 lathe as I expect for that money. The mandrel will be the higher-priced makers say, I shall not get such a 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 care, as an amateur would use a lathe; besides I have not got £70 or £80 to lay out, and it would take me years to save so much, and I want the lathe with as little delay as possible. If, on the other hand, I can get the castings, 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 have the pulley divided, &c., &c. (I could fit them 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 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 under these circumstances?-TOMETER.

[4669.]—OXYHYDROGEN MICROSCOPE.-Can I use my achromatic microscope lenses (lin. and 2in.) with an oxyhydrogen lantern, 8in. condenser, for showing microscopic objects on a screen? A description of the mounting required would oblige, if possible.-E. H. JONES.

[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 appear. ance, and being highly ornamental will cost too much to regild.-W. E. M.

[4659.]-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 the prongs of forks, &c ?-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 lb. No. 16 primary wire, and 1lb. No. 35 secondary wire, gin. long. How much battery power can I use with safety, and how much spark ought I to get without condenser? How long a spark can I expect from a single pint bichromate battery ?-TOMETER.

[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 ?-TOMETER.

14664.]-PRESSURE OF 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 other 8in. diameter for Sft. of its length, the bottom 4ft., are 4in. diameter. Is there any difference at the bottom of the two pipes in pressure per square inch ?-HOLBECK.

[4665.]-PROBLEM.-Would any reader give me a solution of the following problem, taken from the first B.A. Algebra paper, 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 1h. 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 1h. 40m. behind time. Find the length of the line. B. Supposing the above question were varied in the latter part of it by your being informed that had the accident occurred when the train had gone half-way, it would have arrived 1h. 20m behind time;' would that information have been incorrect?" Would it have enabled you to determine the length of the line."BEVERLEY.

[4666.]-LIQUID BONE MANURE.-I shall be obliged if some of our correspondents can tell me how to dissolve bones, so as to make a liquid bone manure which may be used without injury to plants ?-S. W. [4667.]-CLEANING GUN-BARRELS.-Does "Muzzle

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 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 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. W. J.

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

[4683.]-VALVE FACINGS OF CYLINDE J. C. Molton or any other obliging sube if the valve facings of model cylinders whether they are put or brazed on after it g if cast on how is the cylinder finished of? I put anything in my crucible (brass) to a free in casting, and how to avoid the seame going in with it, as it chokes up the mould-ca moulds require to be heated? Thanks to Jo his last instruction on cylinders.-ÁMATITA M FOUNDER.

[4684.]-TYPE.-Would any reader be kind com inform me whether there is any decisive text > tinguish "pirated" from genuine "faces" in typ. whether, if in equal quality of metal, the former serviceable to the printer?-COUNTRY PRINTER

[4685.]-GILDING ELECTRO.-Will some pract electrician give me some information upon whats known to the trade as solid depositing- manais turing solid articles by depositing gold in the way the copper is deposited? Is the solution worked warm or cold? What battery power is used, arranged for gaantity 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? I believe there must be a large quantity of gold in the solation.-W. H. CUFFIN

[4686.]-INSULATION.-TO INDUCTORIUM."—I wish to ask "Inductorium," who describes a mode of making a coil on page 472, No. 173, if he finds the immerlation between the primary and secondary coils sas cient? In coils of the ordinary contruction only a small part of the secondary circuit approach the primary, being the layer next to the reel. In the vetal mode the two extremities of the secondary coil are s rated from the primary by only the thickness of the reel, and from communicating with each other by her that thickness plus the resistance of the primary te tween the two points. In his case the terminals are 1sulated from each other by their silk covering the thickness of the reel, and one of the rings plus the leng of the primary with its cotton covering. This am to only in. solid ebonite, the rest of the res certainly being not equal to fin. of the same. Is d ebonite enough insulation between the terminals da wire giving 3in. and 4in. sparks in air? For his sa certainly hope so.-W. H. COFFIN.

EMULSION."-The above preparations are exces [4687.]" PANCREATINE" AND "PANCREAT cod-liver oil, but to buy them comes expensive. Le medies for indigestion, and are very useful for takiave reader would inform me how I could prepare sashould feel greatly obliged.-H. H.

[4688.)-SEPARATING BEESWAX FROM RES &c.-I should feel greatly obliged if any reader cont form me how to separate beeswax from resin and pa foot oil, with which it has been mixed?-CABINET-MAGS [4689.]-PEDOMETERS.-Would any brother give me a description of the action of the pedomete AN ENQUIRER.

any kind reader will describe the Indian copper coin, the balance? What kind of bow am I to use-it

of which I forward sketch.-COLLECTOR.

circle,draw a chord which will be cut by the circumference [4674.)-PROBLEMS.-a, through a point given in a 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-FISH.-I have a pond in which I keep roach, gudgeons, and minnows. 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.-VIVIS SPERANDUM.

I am

[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 me 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, &c., of a turbine would do? Also what kind of a turbine would be best?-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 subject than Bourne's? If there is would one of your readers tell me the price, publisher, &c. ?-THOS. WATSON.

[4690.]-HOROLOGICAL.-Will some of our be logical friends who are adepts at the use of the give me some practical instructions how I am ceed in turning down the collet of a verge for strength, and string-also what kind of graves use; size of cutting angle it must have, positi speed to suit best; aud, above all, whether it hand in using, length of stroke for the bow, qus, cut with the work revolving to the graver graver? I find in practice that I cannot h progress when I attempt to cut the work re its upper surface towards the graver. All appears to be a mere scrape. But in the ter when the under surface of the work revolves ar the graver I make better progress. In fact Ite quently taken hold enough to break the verge in ba Where is the fault, is it in the bow, the graver, C self?

My friends may judge for themselves d progress when I tell them that it will take me of hard cutting, scraping, and scratching to turn the collet of a polished verge, previous to putti the balance when an adept could do the same was half an hour. I also wish to know how the pivots of pinions are got to the required size. Are they tur with the graver or filed down! I have frequently pu new pinions, but always file them down to the regar size in the turns, by placing the end of the pinion notch at the end of the centre of the turns with end of the rest as a guard, to keep the edge of the t from running away from the shoulder of the pivot. it the proper way ?-SCRAPE.

nus" give me the power of an engine whose cylinder [4691.]-POWER OF ENGINE.-Would "Vertu 2in. in the bore and of 4in. stroke, by the rule he mai the necessary thickness of builer plate, and pressure & steam to work at to attain the power of one horse?R. W.

[4679.]-CIVIL ENGINEERS' EXAMINATIONS.-tains in your last week's issue (1471), and what will be Would some kind correspondent give me a little information about the Institute of Civil Engineers ? What is necessary to become a member? and what is re