surfaces, sleek it with his trowel. If his castings are heavy, he will have to pay attention to a proper quantity of coal-dust in his facing sand rather than use charcoal blacking. For loam likewise his treatment will have to vary greatly, according to the nature and weight of his work; but he will make a mixture of clay, water, charcoal, dust, and salt, or preferably urine, in proportions that only practice in his particular locality can give him, and put it on his mould with a brush or swab and well dry it. But as the sand and loam vary greatly in different parts of the country, so must the blacking put on the moulds to make the castings skin clean. He will find that having his metal neither too hot nor too cold when he casts has very much to do with the cleanness and blue colour, and also if he wishes them to be blue, he must not get them out of the sand redhot.-EDWIN HOLMES. [6120.1-MECHANICAL MEANS OF DESCRIBING PART OF RADIUS.-I presume you mean part of a circle of 80ft. radius (for part of a radius is, of course, a st.aight line). If not for very accurate purposes, take a straight-edged slip of wood, with straight grain and free from knots (a good lath planed will do), which for 80ft. radias will, I think, require in 10in. (from end to end) to be curved 0185in. froin centre of arc to centre of chord.-W. M. F. P. [6120.]-MECHANICAL MEANS OF DESCRIBING PART OF RADIUS.-The easiest is to make a drawing on a reduced scale, and to mark on it the parts really existing, then to bring the principal points on the ground, or on a wooden template, with their respective real distances as found on the drawing.-A FRIEND. [6120.]-MECHANICAL MEANS OF DESCRIBING PART OF RADIUS-I suppose G. Ebden means part of circumference not radius; if so, let him draw his 10ft. straight line, and in the middle of it set off 13in.; then join the point of this with the ends of his base line by straight lines, and then on the middle of them set off on a perpendicular 7-16in. and 1-32in., then let him join the five points he has now got by straight lines, and it will be near enough for his purpose. If the curve looks too much made of straight lines when he has it laid down, I will calculate some intermediate points for him. I congratulate the Editor on the good selection of articles, which are improving. A few more of the class of the "Lessons on the Calculus," which I hope will be continued, and of C. Draper's "Friction," and of letters like letter 1138 on the Egg-sewers," will make the paper the best of practical usefulness and utility.Ром Сноо. [6121.]-ARITHMETIC FOR THE BLIND.-I beg to propose the following contrivance:-A flat board with a certain number of regularly-spaced holes-say one hundred (10 by 10), and a box of characters in it will assuredly pay better to purchase your chickens, since you can procure them at a very moderate price. But why not commence with good stock? Let me remind you that nothing pays so wretchedly as to begin poultry fancying with inferior birds. I presume you have a good wide range, if so, secure a large coloured Dorking or Creve Coeur cock (if from a country yard the better) and mate him with young hens, with plump full breast and low on the legs. A cross between dark Brahma Pootras and Dorkings is not to be despised. I admit the former take somewhat from the delicacy of the flesh of the latter, but make ample amends by the strength of constitution they infuse; and the chickens are of gigantic size. At the age of six or seven months they should be grown enough for the table. The fowls in your possession" with combs in the shape of two horns" are of the French breed-either the La Flèche, Crêve-Cœur or Houdan. You will find them very productive of good sized eggs. Their only drawback is they are non-sitters. To describe the principal varieties of poultry would occupy too much valuable space in "our" journal. I utg to say it will give me great pleasure to assist to my utmost any project for the improvement of poultry either for table or exhibition.-JAMES WALKER. [6125.]-DEXTRINE.-See No. 2416, page 117 of last volume.-BETA. [6125.]--DEXTRINE is prepared by heating commercial starch suddenly to 320, and maintaining it a t this point for some time. Also by heating an infusion of ground malt in water to about 165°, and adding starch in small quantities at a time, as soon as the starch is dissolved the temperature, is raised rapidly to 212°, and the liquid filtered and evaporated with constant agitation until it has acquired a syrupy consistence.-J. G. GRENFELL. [6127.]-CEMENT FOR INDIA-RUBBER TIRES.-I use a cement for fastening the rubbers to metallic wheels, but as it requires the wheel and rubber to be heated to about 150° I am afraid it is not applicable to wood wheels. "Lenox " had better cut some strips of sheet iron, about 18 gauge, of the same radius as his wheel, and screw them to the sides of the felloes, projecting about ths above the tire.-BICYCLE MAXER. [6128.]-NITROUS OXIDE.-In order to produce nitrous oxide" W. J." should neutralize nitric acid with ammonia; the nitric acid is thereby converted into nitrate of ammonia, a crystalline salt, in appearance something like nitrate of potass. Place the nitrate of ammonia in a retort and apply heat, and it will imoxide may be collected in a jar at a pneumatic trough, mediately be resolved into nitrous oxide and water. The whilst the water condenses. In general the respiration of nitrous oxide is attended with no unpleasant results, but it is always safer to have the advice of a medical man before administering it, as in some persons it produces strong convulsions. Care should be taken that the nitric acid contain no trace of muriatic acid, and that the nitrate of ammonia be not heated too strongly whilst collecting the oxide, otherwise the gas will not be pure.-HAWKEYE. [6128.]-NITROUS OXIDE (N0).-1 nitric acid, 1 sulphuric acid, 20 water, digested on ziac; NgO slowly given off. Sal ammoniac and nitric acid (s.g. 1-20) relief, made of lead (fitting in the holes), and of which I gently heated; pass gas given off through caustic potash annex a sketch. I have seen this method employed.-solution. But purest by nitrate of monia heated in BERNARDIN. retort, melts, and between 400 and 500 NgO and steam [6122.1-POULTRY BREEDING.-TO J. MERRI- given off; if heated til white fumes appear in retort it If it is not your intention to have a good breeding stock decomposes explosively.-W. M. F. P. [6128.)-NITROUS OXIDE.-The best method to obtain nitrous oxide is to heat solid nitrate of ammonium to 220 per cent. It may be collected in a gas jar, provided with a stop-cock, over brine or hot-water. If the temperature rises too high, a more complex decomposition takes place, while fumes of nitrate and nitrite of ammenium pass over, mixed with nitrogen, nitric oxide, and ammonia gases. Sometimes this is attended by explosion. When the gas is to be iuhaled, great care ought to be taken that no ammonic chloride is present in the nitrate, otherwise the product will be contaminated with chlorine. The gas before being collected ought to be passed through solutions of ferrous sulphate and caustic soda. One ounce of the nitrate gives 500 cubic inches of the gas. -A YOUNG CHEMIST. [6131.]-ICE.-Ice is safest when it is not broken round the edge, because it adheres strongly to the bank, and is thus kept stretched and prevented from bending. There is an old rule," if it cracks it bears, if it bends it breaks." The general breaking up of the whole surface of the ice in the Regent's Park, three or four years ago, when so many people were drowned, was generally attributed to the fact that the keepers broke up the ice round the island for the sake of the ducks. The effect was like what would happen if one end of the rope were cut, which bears a rope-dancer. Fortunately the keepers did not come round to the back of the island, where I was skating with many others, or there would probably have been more people drowned.-J. G. GRENFELL. [6131.]-ICE.-Being a skater of more than 30 years standing (?) I distrust ice broken round edges. The reason is obvious, it is partially broken already, and the water can too easily escape from under it, so as to allow it to bend to breaking point.-M. P. [6181.]-ICE is safest for skating upon when broken away at the edges. The cause of this is the contraction of the ice, consequent upon cooling below 82, the temperature at which it was formed.-C. E. BRODIE. [6132.]-PLANTING POTATOES.-Potatoes may be planted from the beginning of March to the end of April, or later, but the first week in April is the best time. If the intended sced are not larger than hen's eggs, plant them whole (with the exception of cutting a slice off the tuber to ensure its decay), and if larger cut them into as many pieces as there are strong eyes in the potato. Plant six inches aeep, do not earth up, it is a mistake, and 18in. apart in the rows, and allow two feet or more between the rows. Picking off the bloom will increase the produce, but I never knew it improve the quality.-UN JARDINIER. [6132.]-PLANTING POTATOES.-"Cut from the finest tubers, and cut as soon after being lifted or as long before planting as convenient, with not more than two 'eyes' in each cut, and the cut or set to be as large as the tuber will allow; hence the choice of large potatoes with few eyes. Placed very thinly from frost to green and dry."-"Nothing gained by very early planting."-Vide Gardeners' Chronicle. "The Ground. If retontive and wet plant on the surface, having first put on a heavy top-dressing of soot and lime, together with leaf mould, roasted hedge-clippings, or any halfcharred vegetable matter; then draw this over the sets, mixed with the surface soil, to the depth of one or two inches, and by successive hoeings to three inches."Vide Ingram, Belvoir Castle. On sandy or other light soil, plant one or two inches below the surface in a depression, the "lands" between the rows two or three inches higher than the level, mulching all over with sort stable litter not too rich in fresh manure. Working.-Do not "hill" at any time, but at each hoeing pull over the set the surface soil, and round the plant as much or little as the weather may determine. A Dutch hoe for the first sowing, afterwards a triangular, drawing or chopping towards the rows. Could the coming season be foretold, then your co respondent might be able to say the distance from set to set and the rows. He could not plant too thinly in a wet season nor too closely in a dry one; and this will guide him also as to his local whereabouts:-Kidney for the red soils, round for bog or sand. Should this not be sufficiently explanatory I will write more fully.-ROLAND. 洲 [6134.]-ELECTRICAL.-I send the following, which I think will serve "Colonel B.'s" purpose:-G H is a magnetic needle connected as in a single needle instrument; AB is a bar of metal attached behind the needle and working with it; C and D are connected with one pole of a battery which works the electro-magnets in the receiving instrument; E is connected with one end of the wire of the magnet which turns round the type wheel, and F to one end of the wire of printing magnet, the other ends of the wires being connected with the- end of the battery. If a current be sent through the instrument turning the top of the needle to the left, the bar A B will connect DE, thus causing a current to act on the step-by-step magnet. A current causing the needle to move to the right will cause the printing magnet to act. Thus the transmitting instruinent would have to be arranged to send currents of one kind to turn the type wheel to the required position, when a momentary current in the opposite direction would print the letter.-W. J. SYKES, M.D. [6185.]-DESERT OF SAHARA.-From statements feasible to make a channel from some selected point in made by French engineers, it is assumed to be quite the Red Sea to the banks of the Nile, which it is proposed to pass by means of a number of large iron pipes or culverts lined with brick and cement, laid parallel under its bed, whence by another "rigole" or channel the waters might be conducted to a point whence they would flow by gravitation over the surface of the Libyan Desert, whose contour is said to be favourable to the process. Geologists all declare the Sahara to be the bed of a former sea, and if it be possible to introduce such a mass of water as would successfully contend with the risks of evaporation and absorption on such an arid tract, a most wonderful metamorphosis of the climate and conditions of Northern Africa would ultimately result on the establishment of an inland sea or chain of salt lakes. The hot winds which now plague at intervals the shores of the Mediterranean, would then probably be changed to refreshing breezes.-P. F. [6188.]-VETERINARY.-If "A Subscriber" blisters the horse's knees occasionally he will find it to have the desired effect.-H. FARRAR. [6188.]-VETERINARY.-A surgeon, writing lately to the Lancet, reports that in case of a severe contusion of the knee, resulting from a fall from a bicycle, he treated the injury with the carbolic acid applications now so successful in such cases, and on recovery was surprised to find the originally bare knee covered with a growth of hair, not unlike that on the head of a little child, and with every appearance of permanence. If "Subscriber" will apply nightly to the horse's knee a pad of lint soaked with carbolic lotion, covering same with gutta-percha tissue to conserve the moisture, he will probably be rewarded with the success so entirely unexpected and novel as reported by our surgical friend, and the materials need not cost more than a couple of shillings at most. Please report if trial should be made with success.-P. F. [6140.]-STEERING BY STEAM has been done for some time past, and if I mistake not, a full description has lately appeared in one of the engineering journals. -A. B. B. [6140.]-STEERING BY STEAM.-" Gray's" steamsteering apparatus-a working model of which was exhibited to the members of the British Association on their late visit to Liverpool-was fitted several years ago in the Great Eastern steamship, where its manifest advantages for vessels of unusual length have been much appreciated. The same gear has subsequently been fitted in the "Inman" steamer City of Brussels, where it has given entire satisfaction, and will probably be supplied to other vessels of that fleet. I also understand that the immense new ships of the "Oceanic" line to New York will be furnished with this reliable, prompt, and easily managed apparatus, which is simple in its action, and not liable to derangement, whilst its power is enormous, exerting a consentaneous action on the rudder with that given by the handle to the wheel, which is controlled by very slight force, and is immovable, except by impulse from the person in charge. The inventor prefers that the cylinders and adjuncts should be fixed near the stern of ships, but it will work as effectively from amidships, although the actuating rods or chains connecting with the tiller are thereby multiplied and more labour is involved in fitting up. Ship owners seem to hesitate in its adoption, principally on the score of increased cost, which is about £500 fixed complete, say about 40 per cent. more than the usual expense of first-class steering gear in vogue.-P. F. [6146.]-JELLIES. - Ingredients:- Gelatine, 1oz., soaked in one quart of water for one hour; lb. of loaf sugar, rind of one lemon peeled thin, and the juice of two lemons; three whites, without the yelks, and two of the shells; the whites and shells to be put in last. Let all simmer about five or eleven minutes, until a nice froth rises on the top. Place your jelly bag in hot water, wring nearly dry and suspend between two chairs. Allow the jelly to cool a little in the saucepan, and then pour slowly into the bag, leaving any sediment in the pan. Allow it to run slowly through, pouring back the first droppings. For colouring, a little cochineal. All jellies can be made in this way. Care must be taken not to boil too fast.-A FRIEND TO YOUNG HOUSEKEEPERS. [6147.] HOT DINNER TIN. -If "Anglo Saxon" will get made a small box, say 9in. x 7in. x 7in., and line it throughout with several thicknesses of coarse flannel or other thick woollen cloth, and have one or more square tins made to fit closely inside, his dinner if placed hot in the tins will keep hot for hours. The lining should be about in. in thickness, that for the top might be loose, in the form of a pad, to be laid on the tins. Care should be taken not to fill the tins while in the box, and they should be thoroughly cleaned after being used.-CELT. plainer with diagrams, but on the whole I think you will [6151.]-HOME-GROWN TOBACCO.-In reply to a [6161.]-COMPASSES.-Compasses can be held still trouble in getting the skin properly dissolved; it is first [6175.] -SEPARATING ALCOHOL. Distillation, [6175.]-SEPARATING ALCOHOL.-" C. A still consists of a retort, and a receiver containing a [6177.)-CLEANING JARS FROM VINEGAR.-Use expansion of the water when freezing that bursts the is in error in supposing that the pipes burst during a [6147.)-HOT DINNER TIN.-I know of nothing of this kind equal to the telescopic dinner can of the Germans. It is a boon. Thus: Get an obliging tinsmith, or, are you acquainted with an ingenious journeyman in that trade? He will do. Make three tin cans. The first 6in. in diameter, and 8in. or 9in. deep. Make another, 4in. or 5in. deep that will slide easily, but not too loosely, into the first. Then another, 2in. or 24in. deep, that will slide in the same way into the second, Inside the first, at a distance the depth of the second (and in. more, for the rim of the lid of the first) solder at triangular points little pieces of tin, to sustain the bottom of it (the second can). Solder pieces in the same way inside the second, to sustain the bottom of the third, but with it, as a matter of course, no allowance for lid. rim or ring; let its upper edge be even with that of the second. Have a lid made to fit closely the outer can. Make a small cup, similar to a child's tin cup. On the top of the lid solder a ring of nearly the depth of the cup, and over which the cup (upside down) will easily slide. On the outside of the outer can make a long sheath, into which a knife, fork, and a spoon (handle) will slip. Your have now your can nearly complete. In the space between the bottoms of the second and the first can you may put your soup, tea, or coffee. You may have a partition in the second, one compartment for pudding, the other for bread, &c. In the third and upper one, you can put your potatoes and meat. The cup is for your tea or coffee. Its ring is for pepper, salt, mustard, &c. The upper can, containing potatoes and meat, answers for a plate. But, if you are particular, you can have a small plate slipped inside the lid, with a small strip of tin made like a spring to hold it in its place. The material of the two inner cans need not be heavy. The two inner cans should have two small movable rings, respectively, for handles. There should be small slots in the rim of the upper can, sufficiently to allow [6180.]-CONSTANT BATTERY.-The "Leclanché" the ring handles of the second to bend over it, otherwise cell will suit a "New Subscriber's" purpose perhaps as they would be in the way of the third can to slip closely well as any. It is constant, and has an electro-motive into the second. A well-made can of this description force between a Daniell and a Grove. My description will keep your food warm and cozy. You might, for a of this battery (illustrated) will be found in No. 296 of trifle, have a spirit lamp in your workshop, over which the present volume. This battery is very cheap to you might place your can for a few minutes. Your work; and I can also recommend the improved Daniell female friends, wife, or others, will thank you for this devised by me, and described in No. 299. The sulphate contrivance. One other thing. If the one who brings of mercury cell is constant but costly to work.-A you your dinner is a little sensitive about "carrying a CORRESPONDENT. dinner can," then have a cover made-the inside of flannel; the outside of American cloth. Have it fastened over the top of your can with a button, or tied with tape. The brightness of the can, the flannel and cloth, all bad conductors, will keep your dinner warm for a long time. I could have made the above [6178]-BURSTING OF WATER PIPES. — Water expands in freezing; if it freezes in a full pipe the expansion bursts the pipe, but you know nothing about the accident until the ice begins to melt and shows the crack, hence the erroneous idea that it is the thaw which causes the fracture.-COMMON SENSE. [6180.]-CONSTANT BATTERY.-The querist should have stated the use he wishes to make of the battery, as each form has its merits for spe cial purposes. He will find most of the known forins described in Nos. 267, 269, 270, 272, 275, 277, and the special forms he asked for in Nos. 281, 294 and 296.-SIGMA. [6182.1-RARITY OF COIN.-I cannot trace any coin similar to "Delta's" in my catalogues, and there fore conclude that it is a rare variety, judging also from Hawkins's descriptions.-HENRY W. HENFRET, M.N.S., &c. [6185.] BREECH-LOADERS.-I would advise "C.T." to examine the breech-loading rifles, exhibited in most gun-maker's windows, especially in the city, but must not at same time deter others from giving sketch and description as asked for.-A. B. B. [6189.]-CHAIN BATTERY.-Flannel is used to hold the liquid and prevent contact of the metals, for which purpose the sizes must be attended to of course. From 10 to 20 cells or joints may be used. The end ones having metal plates attached which are applied to the parts required and held there by bands. The arrange ment has not of course all the advantages of Puiver. macher's, and particularly is not easy to clean and freshen up, but can be made more so by not quite closing the zinc cylinders; nor is its action so constant.SIGMA. [6190.]-SMEE'S BATTERY.-Cork is not good for the purpose, nor is it well to use anything at the lower part of the plates, as little particles of amalgam are apt to collect and form a direct circuit, which is very likely the case with "J. S.;" at all events the liquid is retained there and acts on the zinc when removed out of the liquids.-SIGMA. [6191.] - STRIKING PORTIONS OF LARGE CIRCLES.-Through any three points that are not in a straight line "W. W." can readily strike the circulat arc, without knowing either its centre or radius. Call the two points that are furthest apart A, C; the other, B. Prolong the straight lines BA, BC beyond A and C till lines, and cut out out the triangle thus formed, in any they each exceed A C. Join the ends of these prolonged stiff material. If now this be kept pressed against two obstacles at A C while sliding along them, its angular point B can only describe the required circular arc,—and a pencil is easily attached and made to coincide with B. The principle is taught by Euclid, Book III., prop. 1 and 33-E. L. G. [6191.]-STRIKING PORTIONS OF LARGE CIRCLES." W. W." may safely draw straight lines to represent either of the curves he mentions; for the first1 arc lft., rad. 1 mile, will only deviate about- in.and 1,000 the second-arc 8in., rad. 2 miles, about from a right line, being less than the breadth of the 3 100,000 in. pencline he would describe them with. The formula [6202.]-MILDEWED COTTON.-To remove stains process of bleaching, the expense of time and materials of mildew, the cotton should be put through the full for which would be greater than the value of the article spoiled. If you are near a grass-plat, expose the cotton there for a few weeks.-H. Ö. B. [6212.]-ODIC FORCE.-I am not aware of any further experiments besides those of Reichenbach. Mesmerists have assumed that this is the force by which their marvellous powers are exerted, but it is not proved. I may say that entranced subjects often describe appearances around the operator, such as those recorded by Reichenbach. They have done so repeatedly as to myself; and I have also experimented with them as to magnets. But the force is certainly netism, and also of all vital actions. I do not remem not magnetism, though a constant attendant to magber the explanation of table-turning referred to, but have long ago and often given my own opinion of it as the result purely of mechanical impulse given by the actors themselves, unconsciously pressing in the desired direction in consequence of the concentration of their thoughts and wills.-SIGMA. the Indian eclipse (1868) found that the corona gave a [6213.] THE ECLIPSE.-Lieut. Col. Tennant, during continuous spectrum, without dark or bright lines; some of the American observers in 1869 saw a contianous spectrum crossed by three bright lines (some saw only one bright line, others none). The impression somehow got abroad (and deceived the American observers as well as others) that Tennant had seen dark lines in the corona's spectrum. This, however, he explicitly denies. The polarization of the corona's light would prove more or less, according to the nature of such polarization. If the corona's light were absolutely an polarized, it would prove that the corona consists wholly of glowing gas; for though the light from incan descent solids and liquids is unpolarized where emitted in a directing square to the surface, the light emitted obliquely is polarized.-R. A. PROCTOR. [224]-NITRATE OF SILVER fuses easily on heating, and can then be cast into sticks by means of any small brass tube.-A. B. B. [6225.]-GREY BEER.-This fluid, as described by Aroma," ," must have the curious optical property called Fluorescence (resemblance to the mineral Flor) die covered, but a few years back by Professor Stokes, or rather first explained and brought under theory by him, the observers of the isolated facts having been Brewster and Herschel. If "Aroma" will cut up horse-chestsut bark small, and infuse it in water, he will obtain a fluid of similar colour, i.e., like sherry, and clear in transmitting light, but yet appearing grey or blue near the surface where sun or daylight enters it, and nowhere else, nor by candle or fire light. Most paraffine oil is also fluorescent, and so are medicines (whether coloured or colouriess) that contain dissolved quinine. Another peculiar alkaloid called asculine, gives the property to the chestnut-bark infusion. The light of their fluorescence comes from undulations in sun or daylight that are ultra violet, and invisible as light, till these bodies have, by their singular power, altered its rate of vibration so as to render it visible to us and blue. The glass coloured with uranium, commercially called canary glass," is also fluorescent, but renders these undulations green light instead of blue. Electric light, and that of burning sulphur, contain more fluorescible rays than even sunlight.-E. L. G. [6231.]-MAGIC LANTERN.-1. The light may be obtained by forcing a stream of oxygen through a housegas flame. The gas may be conducted by a flexible tube from any burner in the room to a specially constructed jet inside the lantern. 2. Instead of pure hydrogen, house-gas is generally used for the produc tion of the oxyhydrog en light. The bag can be filled by means of a flexible tube from a common burner. To save time it is better to remove the nipple. 3. The jet is placed between the lime cylinder and the condenser. The proper distance between the orifice of the jet and the lime cylinders, and between the light and the condenser, is easily obtained by "ractice. 4. Only properly constructed jets should be used for the above two modes of producing the light. The chamber in the latter or oxyhydrogen jet, is inside the lantern.-L. [6232.]-OXYGEN IN WATER.-As I really know nothing about the action of oxygen in water on the body I cannot give any opinion worth anything; my impression is, however, that oxygenerated water has no particular action beyond that of the usual charge of air contained in drinking water. Boiling water charged with oxygen or any other gas simply drives the gas away, and therefore any charge of gas should be added in the cold state.-SIGMA. QUERIES. [6233.]-THE EFFECT OF METAL ON ICE.-Can any one tell me how it is that a penny or any coin laid on the ice will eat its way in, and if left long enough penetrate to the water? I tried the above frequently during the late frost; and found that silver penetrated much quicker than either gold or copper.-OUTSIDE EDGE. [6234.]-WATER SUPPLY.-Perhaps some readers will help me in the following:-In laying a pipe (say in. lead) from a fountain to a cistern, distance 900 yards, the latter about 8ft. above the level of the fountain, is it absolutely necessary that there should be an air-pipe, and in what part of it? I have also seen two, or some times three, taps in the side of a pipe similarly situated; for what use are they, and is there any way better than another for finding if it (the pipe) is not tight, and find ing the hole?-JOPP. [6235.)-FISH BREEDING.-Do the fish commonly kept in freshwater aquariums ever breed there; if so, what are the conditions necessary ?—AQUARIUM.. [6236.]-SOLDER FOR GOLD.-Will some brother reader kindly tell me the best solder for some thin pieces of 14 carat gold? I have tried tinman's solder, but it mixes with and spoils the gold. The colour of the solder is no object, as the joint will be hidden.-AMATEUR JEWELLER. [6237.] CARPET AND SURFACE DESIGNING.Will some reader inform me how to prepare the paper, and what colours I should use, and what is mixed with the colours to make it look dead, as I cannot get the water-colours to have an even flat surface at all? I have been at the School of Arts for twelve months, but am not allowed to work in tempera or body-colour. I am drawing from the round at present, but am more fond of making designs than copying.-WOOD CARVER. [6244.]-DEEP-SEA TEMPERATURES.-Will any can it and the lamp be procured from any scientific infellow-reader tell me how the temperature at the strument-maker?-F.R.C.S. No. 3. different depths of the sea is ascertained: especially [6259.]TO "SECONDS PRACTICAL WATCHas, like the atmosphere, it does not decrease gradually? MAKER."-Having had a great deal of trouble during Also, what improvements have been made on Brookes's the past week to repair the escapement of a lever deep-sea sounding apparatus, as figured in Maury's watch, I resolved to look through back numbers of the "Physical Geography of Sea"?—T. F. ENGLISH MECHANIC, and in Vol. VIII., No. 200, p. 408, [6245.]-EQUATION.-Will any mathematical con for the year 1869, I find you giving instructions how to tributor solve for me the following equation, which I make a lever escapement, using the scape wheel as have tried in various ways, but cannot get out? your guide; but as the proportions there used have referx2 + y = 11 Į ence to pallets of 10 deg. only, should be glad if you y2 + x = 7) could tell me how I can ascertain 10 deg. pallets from any other, and the size of the roller (I mean the extreme edge; you have mentioned what it is to the ruby pin hole); also how I could make pair of pallets to scape wheel. Should feel greatly obliged.-P.S. Don't go into algebra, &c., if you can help it. Can do vulgar and decimal fractions.-YOUNG COUNTRY WATCHMAKER. [6260.]-VELOCITY OF LOCOMOTIVE.- Perhaps Mr. O'Hanlon would be kind enough to publish in your columns the remainder of his calculation of the velocity of a locomotive in air. I cannot understand the direction he gives by which he says the final integration may be accomplished. By so doing he would confer a favour on me, and, I doubt not, on many others.-JAMES WILDRIDGE. The results of course are obvious.-T. F. [6248.]-RIGI RAILROAD.-I was told that this rail- [6249.]-FOUR POINTS.-Four points being given on a straight line, to construct a square the sides of which produced pass respectively through these points.STUDENT. [6250.]-WRITING TURNING BROWN.-A sample of ink being given which writes black for the moment, is there not a chemical means for testing if the writing will remain black, or if it will become rusty after some years?-GALLNUT. [6251.]-WINDING ELECTRO-MAGNET.-I have nover yet succeeded in finding out the arcana of winding the insulating wire. I wish, for instance, to put coils 4 or 5 deep on a magnet lin. in diameter, 1fin. high, (Fig. 1). If I begin at A, I do not know how to fasten the end; but if I can manage that, and get on to B, what must I do next? To go over to A again will render further winding impossible from the obstacle of the wire at 2. Can I, after reaching B, work down again over RC, cross as before diagonally to the opposite pillar, and so work up to A, repeating the process according to the FIC.2 A---- FIC.I number of layers required? Or if I want to get down UMBRA. [6252.]-ELECTRICAL.-Will your kind correspondents, either "Sigma," Mr. Tonkes, or " Inductorium," answer me these questions? I am going to make an induction coil, the bobbin of which will be 6in. long within the ends, the ends will be 3in. diameter, and lin. bore for the bundle of soft iron wire. The bobbin will be made of ebonite; should it be ebonite where I wind the primary on? And if it is to be ebonite, what thickness should it be? Can you tell me any better dimensions for a coil with 14lb. of secondary, ends of bobbin in. thick? I intend to put three layers of No 12 cottoncovered copper wire, each layer coated with paraffine, for the primary. The primary will be covered with 3 or 4 layers of silk coated with paraffine. Can you tell me any better size of wire, and will 3 or 4 layers of silk, coated with paraffine, be plenty of insulation for the primary? The secondary will have 14lb. of No. 36 silk-covered copper wire, each layer of wire will be covered with silk coated with paraffine, also the wire will be coated with paraffine, and wound on spirally from end to end. Can you tell me any better way to insulate the secondary? Should each wire of the bundle of soft wire-gore be coated with any insulting solution? What length of spark may I expect to get with this coil, and any improvement that [6299.]-DISSOLVING SOLDER.-Can any reader you may think on, with a carbon battery 4 by 3in., tell me of any preparation that will dissolve common excited with bichromate of potash, the battery has 2 solder from gold without injury to the gold itself?-carbon plates and 1 zinc.-THE YORKSHIRE BEE KEEPER. GEORGE. [6238]-WATCH JEWEL.-What is the relative position of a jewel much used in jewelling Geneva watches, called crisalite or crystalite, so far as regards its durability and value as jewelling in a good workman's watch?-J. G. [6240.]-KNIFE CLEANER.-I would greatly thank any one for a good plan of a cheap knife cleaner, polishing two sides at once, if possible. I want one in my family, and I know of many others wanting one. I have asked at the ironmongers, and they have none under about £2 or £3. Can I not make a far cheaper one? would be a great help and convenience.-CAMBRO. It [6241.]-OPTICAL.-A point a 2in. from a spherical convex mirror of 8in. radius represents a luminous point; required a rule for finding a point e on the mirror from which a ray a c will be reflected to an eye, represented by a point marked b 3in. from the mirror and Sin. from the luminous point a, so that the incident and reflected rays may make equal angles with the normal at the point c.-CONVEX MIRROR. [6242.]-SMEE'S BATTERY.-Will Mr. Tonkes oblige by telling me how to prevent the mixture for a Smee's battery from turning black? After making a fresh mixture and putting the battery in for use this often occurs with a sediment, until it has worked for three or four times, and then I have no further trouble until I make a fresh mixture. The proportions are 1 of sulphuric acid to 10 of water. The battery is used for working a medical coil.-A. B. [6243.]-GALVANIC CHAIN BELT.-I am making a Pulvermacher's galvanic belt on "W. A.'s" plan (1077 p. 848) I wish he would tell me what sort of fastening lought to have on the zine and copper cylinder to secure the belt around the middle of the body, and also if I must dip the belt in a solution of any kind previous to wearing it ?-OLD SUBSCRIBER. [6253.]-EXPRESS ENGINES.-Can any reader of mission, dimensions of the new express passenger the ENGLISH MECHANIC give, through it, with your perengines on the Great Northern, Midland, and London and North Western Railways, or any one of them, and also of the Fell railway engine for running over Mont Cenis? Being a driver of express trains on the London and North Western I shall be happy to give any of your readers information on engine-driving, railway signals, the block system, &c.-AN ENGINE-DRIVER FOR 15 YEARS. [6254.]-CLOCK PALLET.-Will some reader give the principles of the construction of a clock pallet?-A YOUNG CLOCKMAKER. [6255.]-ELONGATION OF MERCURY.-Will your "F.R.A.S." explain why the greatest elongation of Mercury is stated by him in his article on the planet to be "nearly 19," while, in his "Lessons on Astronomy," Mr. Lockyer gives it at 29°; also what is the meaning of the "sun's angular diameter," which he, "F.R.A.S., states in his arti le on "Venus on the Sun's Face" to be about 82/?-E. BENTLEY. [6256.]-DISSOLVING GUTTA-PERCHA.-Will some reader tell me the best way of dissolving gutta-percha? LEATHER STRAP. [6257.)-RAILWAY BUTTER.-How can I make railway butter?-OIL MAN. [6258.]-HYDROGEN LAMP.-Will any correspondent say how to construct a hydrogen lamp; and how spongy platinum is prepared, and how it may be kept in working order in damp weather; is it expensive; or V2 70 A [6201.]-ALGEBRAIC FORMULE. - May I take the liberty of asking Mr. C. Draper, through the medium of your valuable paper, if he can kindly inform me how the two formula, D = V2-v2 D = , are obtained, where A is the force ap70 A plied in pounds per ton to a train, friction and gravity; V and v, velocities in miles an hour; and D the distance in miles. They are used in the Engineer of June 18, 1869.—X + Y. [6262.]-BREWER'S QUESTIONS.-Would " Aroma" kindly give a few hints on brewing to a young beginner, as to brewing mild ale from malt and hops only? First, mashing heat; secondly, what heat run into guile; also how often to skim off the yeast, and what heat to run into barrels, as the water I use is extremely hard, and I find a great deal of trouble in getting my ale bright with the use of isinglass. Any remarks which "Aroma" may be able to give will be esteemed a great favour by-A YOUNG BREWER. [6263.]-GLYCERINE v. COD-LIVER OIL.-Will some of your correspondents kindly tell me whether glycerine is a good substitute for cod-liver oil?—A. Z. [6264.] PROTECTING ELM.-Is there any preparation which is good for fresh elm when used for boattimbers ?-OLD TRAWLER. (6265.]-LATHE.-Would it be asking too much of J. K. P." to oblige me with a sketch of double-bearing mandrel and collars for 5in. lathe (same as he described in answer to " Bierlala," query 4546)? I am puzzled as to the way in which collars are fitted on mandrel. Not being able to get a sight of a lathe of that construction is my excuse for asking so much.-ANGLO-CELTIC. [6266.]-ASBESTOS STOVE.-I have a small workshop with gas in, and I would like to contrive to make an could I not put gauze over and asbestos on it? Would asbestos stove. I have a circle with nine holes in; this not give more heat than the gas itself, or perhaps a kink reader would say how an asbestos stove is made? E. FOWLER. [6267.]-GONGS.-A customer of ours had a large dinner gong with a crack in about 5in. long, with several smaller ones radiating from it from in. to fin. long. to have a piece taken out embracing the whole of the This completely spoiled the sound, and we advised him crack, but he wished us to try and burn it; we did so, and the result has been that the instant the hot metal touched it the gong cracked in all directions. I should be glad if any of our friends could give me the why and wherefore of above, and also corroborate me if I was right in advising the piece to be taken out. ARMLEYITE. MR. [6268.]-ASTRONOMICAL EYEPIECE.-TO PURKISS OR "F.R.A.S."-The Huyghenian or astronomical eyepiece is said to be achromatic in itself; what does this imply? Do the rays emerge in an achromatic condition in all cases, whether the incident rays are parallel, convergent, or divergent; or is it only achromatic for parallel rays? Does the pencil emerge always When the incident in a parallel state or otherwise? rays are parallel, as from the sun, would the pencil emerge free from colour and spherical distortion? I shall feel thankful for an answer. Also, would an achromatic object-glass of great focal length (say 100 yards) converge the sun's rays to a single point? If not, how could high powers be used, the focal point of the objectglass being many times larger than the small eyepiece? I find that an ordinary non-achromatic convex lens, of 1in. diameter and 7ft. focus, produces an image of the while another lens same size, but of only about 6in. or sun at the point of conveyance as large as a shilling, 7in. focus, seems to converge them to a single point; how is this?-PERPLEXED. [6269.]-GOOSE QUILLS.-I have a large quantity of goose quills, and shall be much obliged for information as to the best process to clarify them.-T. M. [6270.]-OIL.-An old subscriber to the MECHANIC, being at times in want of very pure oil for certain work, it struck me that I might extract it from some I exposed it for a time to sperm oil that I had by me. the action of frost, which congealed the fatty matter, and left a liquid as clear as pure water. By this I thought I had gained my object, but on applying, I found it contained no oil. The smell of it was like weak spirits of ammonia of commerce. What I extracted was one-third of the original bulk. If this is not an adulteration perhaps some of your able chemical correspondents will explain what it contains, as it may interest many of your renders in the pursuit of knowledge.—FROM A MANCHESTER MAN. [6271.]-PAINT SPOTS ON GLASS.-My house was painted late in the autumn, and heavy showers of rain coming on the whole of the lower window panes are spattered with minute spots of paint which cannot be got off. Is there any preparation that would remove them ?-AMATEUR. [6272.] ELLIPTICAL CUTTING FRAME. — Will "G. W. A." or some other correspondent be kind enough to tell me the dimensions of the elliptical cutting frame, figured page 358. Please say diameter of the disc upon which is marked letter D, also the number of teeth in each wheel. Does the band from overhead motion go round the disc D; if so, I presume it ruas loose on the spindle running through the bar? I may add that I have never seen such an instrument, and intend to construct one from the reply to this question.-TOMETER. [6279.] - ELECTRO-MAGNETIC MACHINE. Will "Sigma" or any other correspondent please to inform me what they think is wrong with my electro-magnetic machine? It has worked all right up to a few weeks since and I cannot now get the slightest shock to pass through it, although I cannot see anything that has altered or got wrong. The magnet is about 8in. long, and the machine used to give a very powerful shock before.-C. E. W. [6274.]-MERCURY.-Will any one of your chemical correspondents kindly refer me to an authoritative statement of the exact weight in grains of a cubic inch of mercury?-K. J. [6292.]-VARNISH.-Can any reader tell me what is it is possible to make Jacquard cards so that they shal the best kind of thin transparent varnish that will stand not be subject to atmospheric influence? It is, don' water, and also be unaffected by finger marks, &c. ?-less, well-known that the cards will expand in a damp PLYMOUTH. room and will contract again when placed in a dry hot one.-A SUBSCRIBER. [6298.]-ANALYZING CLAYS AND CEMENTS.Would Mr. G. E. Davis or "Urban" favour us with an outline of the process usually used to analyze (quantitatively and qualitatively) clays and cements?-J. HICKING. [6294.] - KITCHEN BOILER TAPS.-Is there any kitchen boiler tap that does not leak? There is a growing prejudice against all kitcheners owing to this failing in taps. Is there any objection to fixing taps some inches above the bottom of the boiler, that they may be never empty when fresh water is added. My taps have always leaked after a few weeks' use, and boilers more than once burst through the carelessness and ignorance of servants pouring in cold water when they were empty. [6295.]-TYPE.-How could I clean some types which have got clogged up with the ink without injuring them? -CLERICUS. [6275.]-ELECTRIC LIGHT AS APPLIED TO PHOTOGRAPHY.-TO MR. TONKES.-I will feel much-DELATEUR. obliged if you will fulfil your promise made to a "Country Subscriber" in the British and Foreign Mechanic in May last, with regard to the electric light as applied to photography.-A COUNTRY AMATEur. [6276.]-LATHE APPARATUS, ETC.-To "J. K. P."-I wish to make several of the very useful lathe apparatus described by you. Will you kindly inform me how the spindle and collars are fitted so as not to jam in the lathe drill described Nov. 12, 1869, Vol. X., page 209 ?-A COUNTRY AMATEUR. [6277.]-CHUCK FOR NUT CUTTING. ETC.-I am sorry I cannot understand either the plan or the mode of using this. Would "J. K. P." make a wood model of this, and hire it out at a small cost? I would also ask him to describe from time to time useful work which an amateur may undertake. Before an amateur can invent or design with advantage, he must obtain some command over his tools and apparatus.-A COUNTRY AMATEUR. [6278.]-CIRCULAR CUTTERS.-I obtained one from Buck, price 8s. 6d. It is apparently intended for cutting clock-wheels 24 teeth to the inch diameter, but I could obtain no instructions, nor did I understand that he kept any other kind of circular cutters. I should be glad of a wood model of one or two shapes in which the teeth could be ground when dull.-A COUNTRY AMATEUR. [6279.]-CIRCULAR SAWS, WOOD PLANING AND MOULDING, ETC.-I am about fitting a circular saw to my lathe, but I wish to adapt the platform to cross-cut boards perfectly square. I also wish to adapt it to both planing and moulding, and it appears to me that either the platform or else the saw spindle must rise or fall according to the thickness of the wood operated on. Which plan is best; and can "J. K. P." give a working plan to effect the object? I have "The Lathe and its Uses," but this subject is not treated of. What is the shape of the revolving cutter for planing, and what breadth of wood will it operate on with foot-power, and what is the best mechanical method of holding and guiding the wood?-A COUNTRY AMATEur. [6280.]-"J. K. P.'s" HALF-HORSE STEAM'ENGINE. -Would "J. K. P." give working plans of the little engine he made, and no doubt very justly prides himself on? I should think Truss's patent tubular boiler would be the very thing for amateurs' small engines. Truss, Friar-street, Blackfriars-road, London, should adapt it and advertise in the ENGLISH MECHANIC.-A COUNTRY AMATEUR. [6281.] ENAMELLED IRON. Is there a simple and inexpensive process for enamelling cast-iron; if so, what is the modus operandi ?-WILLIAM GLAZIER. [6282.]-NAPHTHALINE.-One of the products of the distillation of coal tar, regarded a few years ago as waste. Is it still a waste product, or is it used in the industrial arts? If the latter, to what purpose and how is it applied?-WILLIAM GLAZIER. [6283.] COLOURLESS VARNISH.-Would any correspondent favour me with the recipe for a transparent colourless varnish, such as is used on the white wood toys with printed views on that are sold at water ing places?-Dixi. [6284.]-TAKING PLASTER CASTS.-Will any reader tell me what to employ in order to prevent the hair and beard from sticking to the plaster of Paris while taking a cast from life ?-A SUBSCRIBER. 6285.]-GLASS PRISMS.-Will any of your able correspondents explain the method of shaping and polishing small glass prisms of various angles, such as are used in spectroscopes and other optical instruments? -AMATEUR OPTICIAN. [6286.]-PORTER.-Will any of your numerous readers inform me how to brew good porter ?-ONE WHO LIKES IT. [6287.] PAINTING NEW IRON. In painting new iron (say black) should I use gold-size as well as driers, and is the paint sold in tubes suitable? How if the ironwork is a little greasy?-VELOCE. [6288.]-LATHE.-Will "J. K. P." give me his advice on the following? The lathe I think of purchasing will be a 5in. back-geared. Will that be sufficiently strong on the nose to carry a face-plate and a 6in. cylinder cover to be turned? Also a 1gin. crank, those being the largest I should want to turn? Also if I could purchase as good a one in London as in the country as I require no finish about it but good workmanship?J. W. P. [6289.]-ELECTRO-MAGNET, Erc.-Will Mr. Tonkes or Sigma" kindly inform me what size magnet,the legs as short as possible, with single battery, would sustain 201b.? Also at what distance it would attract 2lb. or less? Also what battery would be best for the above, one that would retain its action with little attention for twelve months? Also name some simple work on electro-magnets, &c.-SNATCHBLOCK. [6290.]-COATING BRASS WITH ZINC.-Will any of my brother readers explain the method (if any) of coating small brass articles, such as brass chain, with zinc? I do not want it done by galvanism.-PLYMOUTH. [6291.]-COPPER FOIL.-What is the largest size that copper or tin foil can be rolled (I mean in surface not thickness); also, where can copper foil be obtained? -PLYMOUTH. [6296.]-PORTER STAINS.-How can I remove porter stains from the leaves of a book?-CHASE. [6297.] - ENGINE.I have a condensing engine, cylinder 30in.; stroke 86in.; revolutions 80 per minute; slide valves, one for steam, the other with adjustable screw for cut off. This engine gives a loud knock every stroke, which I have not been able to overcome. putting the valve or eccentric forward I remove the By knock to the bottom, if the valve is put back the knock is at the top and seeins to occur exactly at the commencement of the stroke. The engine is a vertical one, and new. Any information on the subject from my fellow readers will oblige. P. S.-I should much appreciate the details of "Leh Teb's " exhaustion gear, or any other effective means of working cut-off motion by governors.-G. B. W. [6298.]-BRAZIL.-Can any reader favour me with any information about Brazil? I am thinking of going there with a small capital with two other emigrants. I am 26, have no particular trade, yet understand seed and flour grinding perfectly, can smatter Portuguese, and like a warm climate, if healthy.-O. F. W. [6299.]-FRENCH BRONZING.-I should be obliged by Mr. Sulvan explaining his mode of French bronzing more clearly (given on p. 308, No. 5762). I have tried it diameter, made of zinc I believe, the bronzing of which and failed on a French medal of Bonaparte, about 2in. typing. I made a paste with vinegar and the other macame off when trying to make a wax cast of it for electroterials in the right proportion, viz., cinnabar, 48grs. ; Verdigris, 48grs. ; and alum 2drs. each. The paste when made was at first reddish but soon turned black and medal as a handle I washed it as directed, and having then green. Having stuck a cork to the back of the spread the paste thinly and warmed it over a gas burner till dry, I then washed it off and found the medal a dull black. Wishing it to be a more coppery colour I mixed spreading on some more I dried it before the fire and some pounded sulphate of copper with the paste, and washed the dried crust off, but still the medal remained a dirty black, which was not improved by repeating the process. In fact the black colour has come off in several places. An answer will greatly oblige.-FABER. [6300.]-QUININE.-Will some reader give the process employed for the extraction of quinine from cinchona bark, and oblige ?—C. J. M. [6801.]-RECOVERING CYANIDE OF SILVER.-I [6310.1-ELECTRICAL.-Can "Sigma" tell me boy to lengthen the spark of a small plate electrics) m chine; whether it can be done by putting one of those large rings on the conductor? If he can give me a few hints as to how to make one I shall be much obligedS. F. [6311.] - EMERY SAW SHARPENING WHEELAWill some brother reader be kind enough to tell me the cause of my saws being so hard after grinding wit emery that the file will not make the least impression on them? I do not know if the wheels are not drive fast enough or not. The wheels are very smooth, and it takes a long time to do.-SAW SHARPENER. [6312.]-BICHROMATE BATTERY.-Will any read tell me whether the addition of chromie or nitric acid with the bichromate solution in the porous cell rah adds constancy to the current, and prevents the rap falling of the power ?-A CORRESPONDENT. [6313.] LUNAR ECLIPSE. Will some talent correspondent to our valuable journal favour me vita diagram of the eclipse of the moon which took place the 6th inst., and practical rules for drawing ( curved lines) such diagrams for lunar eclipses and taken from the Nautical Almanac, and the projection, occultations of fixed stars by the moon. The dat të le show the beginning, middle, and end of the eclipse o occultation, as in the annual published by the Station/ Company, or other similar works of merit ?-S. DAVIS [6314.] - BOILER VALVE. Would any of you readers oblige me with a description and slight sh of the regulating valve which is attached to some bas by means of which whatever may be the pressure of the steam in the boiler this valve only allows a certa uniform pressure to escape for heating or other pa poses?-VALVE. [6315.]-MISTLETOE.-Will some kind contrilate tell me how to cultivate the mistletoe? I have plenty berries, since Christmas week, and an old apple trein my garden, but I want to know how to select the berries to rub into the bark of the tree. I have be told they are dicecious, and if so, I do not know which is which."-AMATEUR FLORIST. [6316.]-GLASS.-How is a common glass made represent ground glass; and how are the designset clear; is it by scraping the stuff off again or by leav it clear ?-- HOLLYHOCK. UNNOTICED QUERIES. IN future, if any query remains unanswered for for weeks, we shall insert the number and subject of the query in this list, where it will remain for two weeks, not previously replied to. We trust our readers v look over the list, and send what information they for the benefit of their fellow-contributors. Since our last "Artillery Captain" has answered 522 Henry Beadling, 5463; Tometer," 5573, 5615, Beacon Lough." 5694; "Un Jardinier," 5715; W, Exhr "A. B. B.," 5578, 5675, 5676, 5741; "Nobody," 57 5726; "Delateur," 5733. shall feel obliged if one of your correspondents would inform me how to recover the cyanide of silver from the sawdust we use to dry out the works after electro-plating? I am employed in a very extensive firm in this town, and I am convinced the question is an important one to us. I shall be glad to exchange any information I possess for that which I require. I believe the sawdust is burned 5761 first.-AN ELECTRO PLATER. 5751 Casting Brass, p. 261. 5760 Slate, 261. 5775 5783 5789 5796 [6302.]-WEATHER PREDICTIONS.-Will Mr. Albert P. Holden or Mr. Fred. Pratt oblige us with some information about the latter's system of weather predictions? Many readers are much interested in this subject, and will feel indebted to either or both the above gentleme 1 5803 for information.-DER SUNTHAL. Watch Dials, 261. Brazing Steel, 262. Rose-coloured Prominences on the Sun, 253 The Inter-sidereal Ether, 262. Division of Ellipse into Equal Parts, 202. 5798 Violin Pegs, 262. Compasses in Iron Ships, 262 5810 Damp-proof Paper, 262. [6303.]-A CHEAP MICRO-POLARISCOPE.-Perhaps 5816 Soft Soap, 263. your practical correspondent Edwin Holmes will state 5817 Water Wheel, 263. the reason for placing twelve glass plates at 57° for trans- 5820 mission (letter 1125, p. 873). This is the angle for polariza- 5821 tion from one plate, but twelve plates do not give their maximum effect, except at 699 (I see that he eschews !); at 57°, 27 plates would be necessary: the rule is 4184 number of glass plates tan.: of polarising angle for transmission.-W. M. F. P. [6304.]-ANEMOMETER.-I have an anemometer on Robinson's principle which I wish to place on the top of a pole 40ft. high. I shall require two chains from top to bottom to move the clock work below, as the machine is a registering one. Will not the weight of the chains, (no matter how light) cause a great amount of friction, and thus retard the velocity of the cups? Can I adopt any other method? I should very much wish the above satisfactorily answered.-DER SUNTHAL. 5824 Glanders, 263. 5827 Dissolving Silk in Cupro-Ammonium, 23. 5829 Iodine in Milk, 263. 5830 Harmonium, 263. 5833 Elementary Mathematics, 263. 5834 Harp Music, 263. 5837 To Millers, 263. 5838 Alarum Bedstead, 263. [6305.]-MOULDINGS.-I wish to know the proper way to use hollows and rounds for moulding purposes, 5869 wishing to match some old moulding. I am puzzled to guide the planes. Is it usual to nail strips on to the work? 5670 -HANDY ANDY. [6306.] - GALVANIZING BOAT NAILS. Perhaps some of your readers could tell me how to galvanize boat nails for¡ a hooker? I cannot buy them here. They last simplest way would be the best.-OLD TRAWLER. three times as long as when not galvanized. The Model Paddle Steamers, 287 5871 Atmospheric Bells, 237 5880 Magic Lantern as a Photographic Eularging paratus, 288. Black Bronze, 288 Mandrel for Watchwork, 288. 5833 Fastening Marble Slab, 238. 5896 Electrotyping, 288. 5898 Cotton Covered Wire for Bell Ringing, 258 [6307.]-SHOWING OPAQUE OBJECTS ON DISC.Will some kind reader of the ENGLISH MECHANIC describe the apparatus by which the magnified reflection of an opaque object is thrown upon a screen in the same manner as magic lantern and screen ?-H. LANE. [6308.]-GLOBES.-Not being in so wealthy a position as to enable me to purchase a pair of globes, I appeal 5904 through your pages, to some brother correspondent to inform me how I could construct the shells for a pair of 12in. globes, celestial and terrestial.-W. P. B. [639.]-JACQUARD CARDS.-Will one of your nunerous well-informed contributors inform me whether The English Mechanic AND FRIDAY, JANUARY 27, 1871. ORIGINAL ARTICLES. light, from which the well-known flames or pro- Irregularly skirting these, and close up to the moon in the parts where the prominences were ORLD OF SCIENCE AND ART. absent, of a small breadth, and of a pearly or milky-white colour, is a band of light, the ringformed corona or leucosphere. Outside this again, gradually fading away into the cloud, there is yet more of similar light, supposed to be distinct from the leucosphere, but joining or close to it. This is the corona proper, or glory, or radiated corona, as it is variously called. It extended to a distance of almost the moon's diameter from the moon's limb, but not equally in every direction. It had a greater extension in four directions at the extremities of two diameters of the moon at right angles, so as to give it the shape, roughly speaking, of a square with rounded corners. It was broken in parts, and notably by one decided V-shaped gap. This was observed not only by one party, but at the three stations San Antonio, Jerez, and La Maria Louisa; from the description which has preceded, these will be seen to form a triangle, each side of which is five or six miles in length. THE SOLAR ECLIPSE. [FROM OUR SPECIAL CORRESPONDENT.] HE readers of the ENGLISH MECHANIC are already acquainted with the general fate of eclipse expeditions which left our shores in early part of last month; and as it is not essary to recount the incidents in the voyage he Urgent, so well told by one of our ablest ants in the columns of the Times, we may at e describe the operations of the party located Spain. Suffice it then to say that after landat Cadiz, and taking up their quarters, the truments were unpacked on Friday, the 16th, 1 the first adjustments made. The Enga expedition was not the only one in the ghbourhood of Cadiz. The Americans were a y strong party at Jerez (or Xeres), and Lord dsay, with great public spirit, had equipped a mplete party, at his own expense, who were tioned at La Maria Louisa, about five miles st of Jerez. The Spaniards, who have a fine servatory at San Fernando, near Cadiz, sent a rty to San Lucar, a town at the mouth of the adalquiver, about ten miles N.W. of Lord ndsay's position; whilst the English temporary servatory was at San Antonio, intermediate to erto Santa Maria and Jerez, about three miles om the former, and five or six miles from either ord Lindsay or the Americans. Here the bulk the English remained, but others were pruntly scattered about, three with the Americans, o with the Spaniards, and one at Arcos, some enty miles E. by N. of Jerez. The observers re thus made to cover an extensive tract of untry, with the object of obtaining a greater ance of somebody having fine weather, and also cause, in the event of several parties making servations, their scientific value would be rgely increased by the difference of station. he 21st of December was really a fine day, and 1 were in good hɔopes for the morrow, but when e morrow came all was cloudy. However, the ouds were not uniformly dense, thinner patches re and there permitted the sun to be seen, and rough one of them a fair view of the totality as observed. Beyond this are sometimes seen streamers of white light radiating far into space; whether they have any real existence, or are merely objective, may well be doubted; but perhaps it was due to the clouds that they were not seen on the present occasion. Such were the general features of the phenomenon; but, alas! how short-lived. In less time than this description has occupied, the beads, which had disappeared, reappeared on the other side of the moon; the curtain of gloom was spirited away as rapidly as it came; the beads united and formed a thin line, soon to widen into a crescent and obliterate all trace of the glory that had been so briefly revealed. The moon, however, was loth to part with her unaccustomed splendour, and clung to the faintest trace of the corona for perhaps half a minute, and then all was gone. But what were the men of science doing all this time? light of the corona itself, there can be little doubt but that the variety of the observations is due to the variety in the local circumstances; at present there is not sufficient evidence to produce the conviction that the coronal light is in itself polarized. The results with the spectroscope are more accordant. They amount to this:-The spectrum of the corona consists of bright lines; these were seen even during the brief view obtained at Gibraltar- that is to say, the light consists of only certain definite degrees of refrangibility, and therefore comes from a glowing gas. This gas appears to be a mixture of hydrogen with a new substance, a substance which is not recognized as belonging to this earth. It is of a green colour, and appears to exist in the aurora borealis and in the zodiacal light. Its further investigation challenges the skill of our chemists and spectroscopists. Who can tell to what their researches may lead? GEOLOGY IN RELATION TO AGRI- A (Continued from page 390.) ND yet here and there the agricultural praetice of more or less extended districts, is to be explained only by principles such as those I have above illustrated, if not really founded upon or directed by them. I will mention only oneexample. The chalk in Yorkshire, in Suffolk, and in some southern counties, consists of a vast number of beds, which, taken altogether, form a deposit of very great thickness. Now, the upper beds of the chalk form poor, thin, dry soils, producing a scanty herbage, and only under the most skilful culture yielding profitable crops of corn. The lower beds, on the contrary, are marly; produce a more stiff, tenacious, and even fertile soil; and are found in a remarkable degree to enrich the soils of the upper chalk when laid on as a top-dressing in autumn, and allowed to crumble under the action of the winter's frost. Hence in Yorkshire, Wiltshire, Hampshire, and Kent, where the lower chalk lies immediately under the surface, or is found at no great depth beneath, it is dug out of the sides of the hills, or pits are sunk for it, and it is laid upon the land with great benefit to the soil. But in parts of Suffolk, where the soil rests upon the upper chalk, there is no other chalk in the neighbourhood, or to be met with at any reasonable depth, which will materially improve the land. The farmers, therefore, from long experience, find it to be more economical to bring chalk by sea from Kent to lay on their lands in Suffolk than to cover them with any portion of the same material from their own farms. The following imaginary section will fully explain the fact here mentioned:: The scientific object of the expedition was to UPPER MOUTH OF THE THAMES CREEN SAND KENT CHALK PLASTIC CLAY The spectacle was a grand one. The light be me gradually less as the sun was more and ore obscured, and this diminution went on with er-increasing rapidity as the sun narrowed to a in crescent. To the observer with a telescope le corona already appeared, showing the disc of Fourthly, the spectroscope was to be emle moon as a dark object in the sky; the crescent ployed. By this instrument any light presented in diminishes to a fine line, then to a series of to it is analyzed or sorted according to its reolden drops, called Baily's beads; then it dis- frangibility. The light may consist of every reppears as the dark edge of the shadow shudders frangibility intermediate between two given ast in the air at the rate of 20 miles a minute, amounts. This is shown by a continuous spectrum, ghostly curtain rapidly drawn across by unseen no colour being absent, and indicates that the pirit hands. A cold gloomy darkness has in a light comes from a white-hot solid body. Or the aoment, with the last twinkling of Baily's light may consist only of certain isolated degrees eads, been spread like a shrond over the land- of refrangibility; this is shown by a spectrum cape. The darkness is not that of night, for it consisting only of isolated bright lines, only s not intense enough; it is not twilight, there certain colours being present, and indicates that In this section 1 represents the London clay; 3 no rosy tint in the horizon telling of a sun the source of light is a glowing gas. Or there may 2, the plastic clay, which is below it; 3, the upper elow; it has not come on gradually like twi- be a continuous spectrum crossed by dark lines, chalk with flints, rising to the surface in Suffolk ; ight. It is the darkness of a total eclipse! it certain tints being absent; this indicates that and 4, the lower chalk without flints, which is too nust be felt to be appreciated. Such it was with light from a white-hot solid has passed through a deep to be reached in Suffolk, but which rises to clouded sky; had the sky been unobscured, the gas, and that the gas has absorbed some of it. the surface in Kent, where it is abundant, is stars would have shone with all the brightness The results of the first two sets of observations easily accessible, and whence it is transmitted of a clear moonless night. A few planets, how-those namely of the sketchers and of the pho- across the estuary of the Thames into Suffolk. ever, appeared-Venus, Mercury, and Saturn were tographers, as far as at present known, have al- 3. The further fact that the several stratified seen by various observers. ready been given in describing the general ap-rocks are remarkably constant in their general In the midst of all this gloom there stands in pearance of the phenomenon. The observations mineral character, renders this knowledge of the the sky that which all the preparations had been with the polariscope are at first sight perplexing order of relative superposition still more valuable nade in order to observe. Where the bright by their discordance. The subject of the polari- to the agriculturist. Thousands of different beds un was there is now a black object-the moon-zation of the corona is confessedly a difficult one. are known to geologists to occur on various parts o the eye intensely black, not so, however, in It is complicated by the inevitable presence of of the earth's surface-each occupying its own the telescope. One observer had described it as polarized light from the atmosphere; the effect unvarying place in the series. Most of these beds being of a green colour and of a velvety texture, of shining through clouds may be suspected of also, when they crumble or are worn down, produce and this description was verified on the present affecting its character. These atmospheric and soils possessed of some peculiarity by which their occasion. Outside the moon-but known, from cloud effects are different at different other evidence, to belong to the sun-was the times. What-affected, and these peculiarities may generally be sierra, or chromosphere, a rim of reddish-yellow to the observed in soils formed from rocks of the same even at the same place at different places, and general agricultural capabilities are more or less ever, then, may be the case with egard |