Oct. 14, 1881. ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 864. nary paraffin burner is soldered, b is a coni-block at one end in which two large holes are IMPROVED LATHE. COMBINATION -II. [19314.]-IN continuation of my description in last week's issue of the new combination lathe in 137 Fig. 8 shows an adapter, c, consisting of a tan- If, now, an eccentric cutter-holder, g, be placed on the drill-spindle, and the requisite adjustment for the pattern be given to the graving-point, and the drill-spindle be also moved to one side of the centre of rotation of the work as may be required, by the aid of the change-wheels, various relations of speed of rotation between the drill-spindle and the work can be arranged, and the eccentric cutter and work be driven at different speeds in the same Fig. 5, I now illustrate a modification designed arbor. In Fig. 7 the drill is shown brought to the be fixed to the top of the slide-rest, a great variety The graving-point will or opposite directions. Fig. 9 shows a further modification, then produce the ovals, triangles, inside and outside loop patterns, &c., produced by the geometric chuck. which will enable work to be ornamented round the edges or at any angle by the drill, and within certain limits by the eccentric cutter. In this case the bracket K can be set to any angle, and hold the work in any position under the drill-spindle, and is clamped by the nut H; the work is rotated screw j. It will also be possible to cut volutes and by the pair of bevel wheels kk. The bevel on the collar. of the bracket K is driven by the tangent spirals by traversing the drill by the leading screw with a requisite speeding between the leading screw and the rotation of the work. Next week will be described some simple arrangements for shaping with small plain Mathes. J. A. Armstrong. CARBON DISULPHIDE. about 450° F. The gas is then passed through the This impurity is now extracted by means of cal- purifying boxes, which are charged simply with means of the reaction between the sulphuretted ammonia, sulphuretted hydrogen, or carbon disulcium sulphydrate (CaH,S), which is prepared by animal charcoal. The gas will then contain no hydrogen in the gas and lime, according the follow-phide, and merely a nominal amount of sulphur amounting to 2 or 4 grains per 100 cubic feet. Of course, when the removal of the carbonic acid is desirable, the gas can be afterwards passed through lime in the ordinary way. ing equation. = CaH2O2+ 2H2S CaH,S2+ 2H2O. (Concluded from p. 117.) SULPHURETTED HYDROGEN. [19315.]-THE next part of the process is the removal of the bulk of the sulphuretted hydrogen, which is effected by some convenient form of hydrated ferric oxide--preferably that which is termed "natural oxide." There is also another form in use called "artificial oxide." For economical and practical considerations good natural oxide is the best, being both cheaper and more efficient than the artificial. Natural oxide of good quality should contain at least 65 per cent. of iron, calculated as FEO,,H,O, and is of indifferent quality when the hydrated ferric oxide falls as low as 50 per cent. These percentages are for the material dried at 212° F. The usual quantity of moisture at 212° is 50 per cent. Artificial oxide often contains anhydrous ferric oxide which is inert with sulphuretted bydrogen. It is usual to lighten the natural oxide with about one-fourth part, by measure, of sawdust or refuse from tanneries. Artificial oxide is already mixed with sawdust by the manufacturers. Oxide works best when in a tolerably dry condition. It may be necessary at times when it gets very dry and dusty to water it down and turn it over, but no more water should be employed than is needed to prevent the oxide running through the sieves. The depth of material in each vessel is 36in., disposed in six tiers of 6in. each. This will give a capacity equal to 42 cubic yards of oxide for each vessel per million cubic feet of gas per diem. The quantity of oxide fouled per million cubic feet of gas is a variable quantity, ranging from four to eight yards, and averaging six yards. The average time each vessel will run will therefore be seven days. The following are the advantages claimed for this process: Freedom from nuisance; the spent charcoal having but a very faint smell, similar to that possessed by oxide material a few times used. CaHS, and CS2 = CaCS, + H,S. There is no washing required, which is a trouSince carbonic acid attacks both the calcium sul-blesome operation, and is detrimental to the illuphocarbonate and sulphydrate, it is necessary that minating power. the gas be well freed from that impurity before The process is continuous; the labour being but entering the third pair of vessels. The same remark nominal, since the vessels containing the charcoal applies, with even more force, to oxygen. How-require cleaning out at very long intervals. ever, if one of the oxide vessels be well fouled, the As a means of sulphur-purification, it is superior iron sulphides therein will be sufficient to arrest the to the process at present in use, as it easily reduces further progress of oxygen. For this purpose it is the obscure forms of sulphur one half. well to so work the oxide purifiers that there is as much foul oxide in action as is consistent with the due removal of the sulphuretted hydrogen. These vessels are charged with 6 tiers of 5in. of lime, which can be fouled at any convenient opportunity. It will not always be needful to work both vessels, one being amply sufficient to reduce the sulphur to 8 to 10 grains per 100 cubic feet. The other vessel can be reserved, ready fouled, in case of an emergency. The amount of work done by calcium sulphydrate is enormous, if the vessels are well protected from the action of air and carbonic acid. The following is an estimate of the cost of this portion of the process : :05 yard lime at 8s.... Labour for slaking, preparing, char- say.... 4.8d. 4 It is asserted by Mr. Lees that there is a gain of per cent in bulk beyond that due to the I per cent. of air. Personally, I am unable to say more than that there is a perceptible increase in volume after the gas has passed through the charcoal. Mr. Lees, who is engineer to the New York Gas Company, informs me, when water-gas, which is largely charged with naphthaline, has been purified by his process, that the objectionable hydrocarbon is conspicuous by its absence. Altogether, the invention, which is covered by many patents, is full of promise, and will, no doubt, take a prominent place in gas-manufacture; especially where sulphur purification without nuisance is a desideratum. The whole of the ammonia is found in the charcoal, combined principally with sulphuric acid, and can be washed out from time to time in a concentrated form. The charcoal accumulates in Course of time a large percentage of sulphur, which is recovered by a process that also revivifies the charcoal so as to admit of its re-use. Beckton, London, E. Lewis T. Wright. CONTINUOUS BRAKES RETURNS, that, with regard to the statements of the Brighton [19816.)-I NOTICE in your article, p. 77, you say and Midland Co.s, you "fail to understand" how THE LAST TRACE OF SULPHURETTED HYDROGEN. The fourth and last pair of vessels should be worked with clean lime, six tiers, with 4in. on each tier, making a capacity of about 28 yards for each vessel per million cubic feet of gas. It is important to allow as little sulphuretted hydrogen as possible to enter these vessels. They can be worked one after the other, or separately, or one To revivify the fouled oxide, as it is termed, it is gency. Since the tests employed for sulphuretted alone with the other as a spare vessel for emerabout a foot off the ground) in a layer about 9in. found difficult, especially during hot weather, to spread on a floor composed of old sieves (placed hydrogen are, in most cases, very severe, it will be the Westinghouse brake works so well on the one thick, and in 48 hours it will be ready for re-use.keep the gas absolutely free from that impurity. The space required for revivification will therefore When the vessels are emptied, it will be necessary be 1520 square feet per million cubic feet of gas. The reaction between the sulphurretted hydrogen and the hydrated ferric oxide is variously represented by different authorities, as occurring by either of the two following equations (neglecting water of hydration). or, FeO3+3H,S= Fe2S, + 3H2O. = Fe2O3 + 3H2S 2FeS + S + 3H2O. The author has reason for believing that both reactions occur, though the former predominates. The following table, showing the manner in which oxide accumulates sulphur, may be of interest : line, and so badly on the other. If you will allow me a small portion of space, I will explain. On Midland it is indeed "carelessly treated." You the Brighton they look after the brake, but on the mention one case where the triple valve froze on the tender; now the water ought to be let out of the bottom cup of these valves every now and then: in this instance it had not been done, the water then froze; hence the failure. Another case, on January 29th, I can also explain. The express was made up of two engines, and equal to 19 vehicles; there were no brake-blocks on either engine-wheels, and the five front vehicles were all fish-vans, having of the second engine put on his brake very sudbrake-pipes only, and no brake-blocks; the driver denly, and before the leading man had shut off steam. Now, Sir, you will see that as the fish-vans had only pipes, all the brake-power, with, the exception of one tender, was at the rear of the train, ging, emptying, &c., 14 yards at 2s... 33-6d. and when I tell you that the couplings of the G. Or say per thousand feet ⚫03d. and S. W. vans were afterwards found to have had The total cost of purification for gas made in the laws half through the iron, you will not wonder metropolis is about one penny per 1,000 cubic feet that the train broke loose. The great delay was of gas, but in one case it is as low as 6d. per 1,000. not caused through the brake, but in consequence The foregoing process is effective, and can be of the "signalman " not allowing the engines to depended upon if care be used to protect the sulphy-return into the tunnel to fetch the train. No doubt drate vessels from the action of oxygen or he acted for what he thought safety, but he caused carbonic acid, and can be conducted without a very great unnecessary delay. Labour for slaking, preparing, char A case in which oxide was worked on unwashed causing any great degree of nuisance. Of course, gas, gave following results : there must be a certain amount of unpleasant It is not at all doubtful that this rather 90d. 15d. .105d. A Driver. SIX COUPLED TANK ENGINES. 119317.]-I NOTICE in your issue of this week a letter on the subject of Metropolitan District engines, from "E. L. P.," in which he suggests a type of engine for working that line having sixcoupled wheels, and a pair of trailing wheels with radial motion. It may interest your correspondent "E. L. P.," and your readers generally, to know that on the L. and Y. Railway engines of the above type have been used since the early part of 1880. The first were four rebuilt goods-engines, Nos. 22, 26, 30, and 333, each having six wheels coupled, 4ft. 10in. diam., and cylinders 15in., 15in., 16in., and 16in. had new boilers and a pair of trailing wheels added, diam. respectively, and 24in. stroke. They have which are fitted with Mr. Webb's radial motion The tanks are at the sides and the back. In proof of the satisfaction these engines have given, new engines of the same type have been built in two classes-one for local passenger service with driving wheels 5ft. lin. diam., and another for shunting with smaller coupled wheels. The cylinders and wheel-bearings are inside. One of the three engines sent by the L. and Y. to the Stephenson Centenary Exhibition was of this type. C P STATICAL PROBLEM. [19318.]-No algebraic solution of the general problem (18838) is possible, as it depends on an equation of the sixth degree for any particular case, however, the coefficients occurring in this equation can be calculated and the solution then obtained by any of the known methods of approximating to the roots of an equation; but the necessary calculations are very long and tedious. The mechanical condition is W1 cos. 6 sin. λ = W2 cos. sin., ช when A, D are the points from which the weights W1, W. hang, B, C the points (in a horizontal plane) to which the string is attached, and a, 3, 4, & the internal angles at A, B, C, D. If BC= a, CD = 6, DA · = c, AB = d, we have the geometrical conditions a2 + b2 — 2 ab cos. y a2 + d2 2ad cos. ¿ = c2 + d2 2cd cos. a b2 + c2 2be cos. d, so that the mechanical condition becomes bW, sin. 8 (a2 — b2 — c2 + d + 2be cos. 3) dW, sin. a (a + b2 — c2 — de + 2cd cos. ). Now we have by projections BD sin. BO cos. BDC + DO sin. BDC BD cos. = DO cos. BDC BO sin. BDC, when BO is drawn perpendicular to DA; hence we can express sin. ồ and cos. § directly in terms of x, since BO d sin. a, DO = c d cos. a, BD2 = c2 + d2 2cd cos. a, 26BD ccs. BDC = ba + BD, sin. BDC = 1- cos. BDC. If we put these values in the above condition and take c2 + d2 - 2cd cos. a=e, instead of simply cos., as the quantity to be directly determined, we get the equation = 1 3 where P " are known functions of a, b, c, d. A real value of e, and so of a, can thence be obtained by Newton's method of approximation, and 6,, are then given by the geometrical conditions. Long as this exact calculation is, it is not really longer than that required by "M.I.C.E.'s" method of solution (19041); for in the latter the magnitude of one of the angles has first to be approximately determined by a tentative graphic process, then the magnitude of another has to be approxi mately found by a method of approximation which is long if a certain quantity H is not large compared with another quantity 2A which may range between 0 and , and then a series of nearer approximations, alternately to the two angles, is to be made. R. E. B. PRODUCTION OF ELECTRICITY IN (19319.]-THE difficulty which "W. T. R." (19231, p. 66, and 19292, p. 116) finds in explaining the source of electricity from a gas-coated plate arises from a very common cause: it arises from observing without measuring. Whatever debate may exist as to the theoretical source of electricity, contact or chemical, one thing is certain, currentthat is, motion of electricity, can occur only with expenditure of energy, and that energy must be derived either from chemical action, which gives up energy, or from surrounding space by means of a lowering of temperature in the liquids themselves. work upon such a scale as permits exact measure-form of deduction, be placed nearer the edge, also FORMS OF SPECULA. Before dealing with the form required, I must Next, we come to the question of the best form to resist flexure. Suppose we assume the speculum to be divided into a number of sectors-say, a dozen, then each of them will be nearly triangular in shape, and therefore the centre of gravity of each sector will be nearly at one-third the radius from the outer edge. Consider the centres of gravity to be connected by a ring, then the radius of this ring will be two-thirds the radius of the sector or of the speculum. In Fig. 1 let SS be the REPLIES TO QUERIES. In their answers, Correspondents are respectfully requested to mention, in each instance, the title and number of the query asked. [44266.]-Kites (U.Q.)-The principles involved in the flight of the paper kite were the subject of investigation by the mathematician Euler, who published his investigations in a memoir inserted in the Transactions of the Academy of Berlin for the year 1756. The subject involves several questions, which for the most part cannot be treated without the aid of the higher analysis; suffice it for the present to state, that the angle which the face of the kite must make with the wind, supposing that to be blowing horizontally, in order that it shall rise with the greatest facility, must be 54° 44'. M. Euler also found, from his calculations, that the tail contributed essentially to the elevation of the kite. There are some chapters on the subject of the construction of kites in Cassell's " Popular Recreator," Parts 4 and 5, which might afford "Ventosus" some of the information he requires. A kite may be made of almost any form provided it be made to balance, that is, not only of equal weight on each side of the points to which the cord is attached, but also to have an equal area of surface. China is the great land of kites; they are a source of great interest to that ingenious people, who have (I have somewhere read) a sort of kite flying festival, when the sky will be peopled with all manner of strange forms of animals, men, birds, fish, dragons, &c., for a Chinaman will make a kite of any form, and having made it, will make it fly. I recollect a friend making a kite many years ago, of hexagonal form, about 6ft. across, which flew remarkably well. As good a form as any, and perhaps as convenient for taking to the scene of operation, is made by taking two light strips of wood, of lengths in the proportion of about 10 to 7, pivot the shorter in its centre to the longer one at a distance slightly more than half the length of the shorter from one end of the longer; the short lath turning round on the long one, the calico covering rolled round them makes the kite in a convenient form for carriage. The calico is attached permanently at the head and foot of the kite, and at the extremities of the cross lath by tapes to tie and untie. As to practical uses, kites. have been employed to lead a line over otherwise inaccessible places, to ships in distress, over the tops of high buildings, &c. Pompey's Pillar was once ascended by a party of sailors by help of a kite, and I believe the vane on the spire of Salisbury Cathedral was once reached in like manner, and repaired. A kite in the form of a hawk is sometimes employed by sportsmen when birds are too wild to be approached; they will not take wing while it is hovering over them. Everyone has read of Benjamin Franklin and his electric kite.-W. W. Now, when we insert in a liquid a platinum plate of this form (see Fig. 2), where the speculum is/As mine was so severe a case it took some time to [44460.]-Eczema.-I would very strongly resection of the speculum, then the position of this commend hydropathic treatment for this comring will be that marked by the arrows T T. plaint. I have been a sufferer from it from childAgain, we may consider each sector as a beam hood, and got little permanent relief till about ten balanced at its centre of gravity, and tending to years since, when almost as bad as I could be, deflect at each end, and to counteract this tendency with my face in a perfectly frightful state, I placed we must introduce the stiffening-rib, as in a bracket or corbel. We thus arrive at a speculum myself under hydropathic treatment at Matlock. coated with a gas opposed to another plate con- shaded by oblique lines and the brackets by ver put right, but in four months I left perfectly free from the disease. I have had several relapses since sidered neutral, we have many phenomena to con- tical ones, TT being, as before, the supporting-indeed, I do not think it likely anything will get sider. The liquids inevitably contain dissolved ring. As a final step, we may assume the brackets the tendency to the disease out of the system, but I gases; if sulphuric acid is employed, it is pretty to become so numerous that they are continuous find a few vapour-baths taken at home, without certain to contain either sulphurous or nitrous acid: round the speculum; the latter then assumes the much trouble, ward off or cure an attack. In the in fact, there are numerous chemical actions possi- form of Fig. 3, which is that suggested as the ble to be set up under the conditions created by an stiffest obtainable with a given weight of material. winter of 1879-80, I had a severe attack in both electric circuit. When "W. T. R." says, The If made of glass, the speculum might, I suppose, arms, but the vapour-baths soon began to take gas seems to be transferred, thereby producing be cast of this form; but if of metal, I think it effect, and in a very short time I was all right electricity," has he examined whether this is the woud be necessary to cast the speculum of equal address, I shall have pleasure in sending partiagain. If "An Old Sufferer" will advertise his fact? Is the new coating of the same nature thickness, and to solder on the extra backing, so as culars of the simple arrangements I have for getting the first? Above all, is it equal in quan- to avoid the porosity which (I am informed by tity ? This last would be the case, if it "A. J. S.") always shows itself in such cases if the vapour-bath at home without special apparatus. were a transfer only, whereas a chemical action back differs much in section from the face. I have might very possibly absorb half and transfer half, observed the same thing in cast-iron work, such as or other proportions. Such examinations are ex-in pipes with bands cast on them. Whether the tremely difficult, because the action is so infini- form of speculum now proposed should rest contesimal. The oxidation of one-hundredth of a tinuously on this ring, or whether the latter should grain of hydrogen would maintain a current for itself be cut away so as to leave merely a certain hours, or even for years, which our instruments would easily make manifest, and even sure. number of equidistant points of support, is a matter mea- for trial rather than theory. My letter is too long to allow me to touch on the effect of edge support (as when telescope body is horizontal, or approach ing that position), but I hope to refer to this in another letter. Therefore, the observation that no fresh chemical products appear, amounts to nothing. No test would indicate the presence of products resulting from what would be considered a large current. It is useless to attempt to base theoretical ideas upon infinitesimal actions. We must To save myself from criticism, I suppose I ought to say that the ring might, under another [44493.]-Nominal Horse-Power.-Does not "Arithmetical Ignoramus" see that I cannot give the definite meaning of N.H.P. inside the shops without being acquainted with the special rule worked to; and I assure him I have not that knowledge of the trade. The so-called Admiralty rule is to multiply the square of the diameter in inches by the velocity in feet per minute, divide by 6,000, and the product is N.H.P.; but, as I said, it is utterly useless, and is not used by engineers. The construction of an engine does make all the difference in the world. For instance, in the case in question-a spinning-mill—it is of the first importance that the engine should run class, built by the Vulcan Foundry Company, 1872. [44694.]-Faulty Common Pump.-I read your paper regularly, but never venture to answer queries unless I know the advice I have to offer is sound. I shall not argue with "Working Tom" as to the usefulness of an air-vessel, but merely tell him that I have cured several cases exactly like his by ordering the use of such vessels, and one, no longer ago than last week. Of course, a portion of the air is pumped out. The vessel would be of no use unless it were so. His assertion that a good suction pump will draw easily 27ft. may be accepted with a grain of salt. A single reciprocating pump, at that height, requires to be worked very slowly and carefully. If a quick stroke is given, the result is a jerk and a smaller quantity of water than is due to the stroke. I should evidently be wasting your space by offering him further arguments as to my simile of the iron or wood rod.-W. WYATT. [44600.]-Huntsman and Cast Steel (U.Q.) -The following is the story of how this inventor's secret was stolen :-About the year 1770 a large manufactory of this peculiar steel was established at Attercliffe. The process was wrapped in secresy by every means which the inventor could command. None but workmen of credit and character were employed, and they were forbidden to disclose the secrets of the process by a stringent form of oath. At last Huntsman's secret was stolen in the following manner:-One night in winter a traveller, to whom the desire of placing himself close to a roaring fire seemed a reasonable request, knocked at the door of the factory. A workman [44698.]-Novelty.-I am exceedingly obliged presented himself, whom the wayfarer addressed to f. H. Wenham for his information on the subhumbly, begged admission. "No admission here, ject of tuning steam-whistles. "Sunlight" proexcept on business," was the reply; but on scan-mised me, on page 47 of our present volume, that ning him over, and discovering nothing suspicious if I would decide as to the number of whistles or about him, granted the request, and let him in. Feigning to be worn out with cold and fatigue, the pipes, he would put me in the way of carrying out the necessary arrangements. Will "Sunlight" wayfarer sank upon the floor, and soon appeared kindly fulfil his promise, and oblige?—G. FRYER, to have gone to sleep. To sleep, however, was far from his intention. He closed his eyes all but two little chinks, and through these little chinks he saw all he cared to. He saw the workmen cut the steel in pieces, and put them in a crucible, and through the entire process, which of course was easily remembered, and poor Mr. Huntsman's secret was no more.-JACK. [44614.]-Dirt-Stains in Wood. It cannot be done. You can try washing with chloride of lime solution and a small brush, but it is doubtful if you will succeed.-T. P. [44616.]-Home Binding.-Most probably the statement is only a puff-especially as it is said that each number can be added in a moment, and that "no back is needed."-J. T. M. [44618]-Shelling Wheat.-I believe it is run through rollers which just crack the shell. The process is somewhat similar to that adopted in the case of pearl barley.-OBERHOF. T. P. Swansea. [44724.]-Heating Railway Carriages with Acetate of Soda.-In reply to "Old Mechanic," the following, translated from Il Giornale del Genio Civile, of December, 1880, may be useful. A plan for heating railway carriages with acetate of soda, invented by Mr. A. Ancelin. is now being tried on the railway from Paris to Havre, and on that between Orleans to Chalons. This system is based upon the fact that solid bodies, in passing to a liquid state, absorb an amount of heat which is rendered latent as the body is dissolved, and on reversing the process and passing back to a solid state this heat is rendered sensible. The crystallised acetate of soda, C'H O'NaO+ 6HO melts at a temperature of 59° cent. (139° Fah.), with an expenditure of about 94 calories, as shown by following formula: = latent heat. 1 = (160+) (C — c) t = temperature at melting point. solid state. [44620.]-Lifting Machine.-" Country Mill-C wright" will find it advantageous to give his c = sieves a combined movement-that is, sharp move- A foot-warmer of the capacity of 11 litres (2:42 ment lengthwise with a slower shift sideways.-gallons) would contain about 15 kilogs. (331b.) of acetate of soda, and supposing its initial temperature to be 80° cent. (176° Fah.) or that of the ordinary hot-water heater, in cooling from 80° to 60° cent. (176° to 140° Fah.) gives....... 225 calories. Latent heat Further in cooling from 60° to 40° cent. (140° to 104°) [44626.]-Staining White Pine Floors.Would "Furnishing Salesman" kindly make his reply on page 22 a little more definite by saying what the" bit of brown umber" is to be rubbed into, the floor or the cloth? Also what "stiffing" with polisher's glaze means?—W. B. [44628.]-Marking Paper without Ink.This querist requires something like Bain's chemical telegraph, a description of which he will find on p. 214, last volume.-E. G. M. [44643.]-Scavenging Machines.-There are plenty of road-sweeping machines in use in London. They have a revolving brush, which delivers the mud, dust, &c., into a trough that is emptied here and there for the heavy carts to take away.-S. M. [44660.]-Organ-Bellows.-Cut out the ribs in paper, and you will soon see what shape they ought to be. The lines showing the gusset corners should diverge. Shown many times in back numbers.-S. R. [44664]-Greenhouse. This question was fully answered in an article on p. 175, last volume. The best angle for latitude of London is 37°.-ONE WHO LOOKS IN THE INDICES. [44631.]-Waterproof Cloth.-In this case it is most likely the cloth was prepared by one of the processes the principle of which consists in rubbing the wrong side of the cloth with a substance such as beesewax, which is then drawn on to the fibres by ironing the cloth on the right side. The alum and sugar of lead process is objectionable on account of the smell when wetted. J. O. [44640.]-Size for Orange Lead.-It would be interesting if "L. E. J." would say what he means. Size of all kinds is simply gelatine, and he can surely try whether isinglass, glue, parchment, or the so-called patent size answers best. He might add a little bichromate of potash with advantage.-T. J. M. [44672.]-Midland Engines.-To "METEOR." -A few corrections require to be made in reply on p. 95. Engines 5 and 21 are double-framed, of what we call the 890 design. No. 610 was built by Sharp, Stewart, and Co., 1867, not by Kitson. No. 444 is a straight-framed goods engine, built in 1860. No. 770 was built by Dübs and Co., 1870, and is a goods engine. No. 920 is the same class and maker, but built in 1871. No. 990 is the same 1,410 96 [44730.]-Electro-Magnet.-An electro-magnet to pull 101b. a distance of lin. will have to be a strong one-the distance is great; for instance, an electro-magnet to pull 101b. at lin. will pull 610lb. For this you would require an electro-magnet having a lin. core, 20in. long, bent into a horseshoe, and having 24 layers on each leg of No. 20 silk or cotton-covered wire; the length of each layer should be 6in. With this magnet and three quart Bunsen cells, you will do what you wish easily.-W. J. LANCASTER. [44734.]-Lecture Experiments.-Gat the 1s., and contains a lot of experiments that may be "Intensity Coil," written by "Dyer"; this costs easily performed. Then you should get a recent edition of Lardner's "Electricity and Magnetism." The descriptions in Lardner's are, very easily fol lowed.-W. J. LANCASTER. LIGHT."-You can utilise your present case if you [44738.]-Exhibiting Photos.-To "SUNfollow the plan I now propose. Across the centre you would require a wood roller of such a size that either four or six flats can be formed on it, as shown in the sketch. These must be the width of the pictures, and the views must be cut to one standard size. Cut out as many pieces of cardspecific heat of acetate soda in its liquid state."board as you have views, and carefully paste a view on each. Next get a band of linen, the bottom ones, also allowing it to hang, as shown, length to pass round both the roller A and the two very loosely. The band then will be wound round by the roller holding the band by the cardboards, resting on the flats. So far, you will need little To get anything like a good effect you will need expense. Next comes the question of the lenses. good lenses, and these should be the regular achromatics, and carried in mounts similar to an opera-glass, B. If that be too expensive, then they may be mounted in an inferior way by a sort of drawer arrangement. The roller must be of such a size that the views must be about 6in. from lenses, as that is the standard lenses. You will, if you wish to allow six distance of the focal length of the required persons to look on at the time, require six distinct bands and sets of lenses, and the bands and lenses must be so arranged that each set of lenses has its own band of views. The achromatic lenses can be bought cheaply enough. Small ones can be got at about 3s. 6d. per pair by buying from the makers direct on the Continent; and if it would be of any help to you, I would be very happy to put you in the way of obtaining them.SUNLIGHT. 1,731 calories. From: 10° to 40° cent. (50° to 104° [44739.]-Vernier.-Full instructions to make vernier, and how to read it, would occupy a great deal of space, and it is doubtful if they would prove intelligible to one who had no knowinformation he wants in "Heather on Mathematiledge of the subject. T. B." will find all the cal Instruments," published in Weale's series, to be had for 1s. from any bookseller.-X. [44741.]-The Sun's Longitude.-Mr. Herschel having given me the clue, I notice-what I ought to have seen before-that the Sun's latitude Fahr.) 30 x 0.32 × 15 144 calories depends upon the position of the Moon, and there = 96 40° to 60° cent. (104° to 140° 30 x 0.75 x 15 337 fore that any irregularity of longitude would probably arise from the same cause. I am inclined to think that "A Fellow of the Royal Astronomical Society" was indulging in a little mild chaff at my ignorance. Well, we old sailors have sometimes had our laugh at the astronomers. I remember, between forty and fifty years ago, being in a flagship on her way to a distant station. On her stopping at a southern port, where was a famous observatory, our navigating officers visited the astronomer, when the conversation naturally turned upon ascertaining the longitude at sea. A young astronomical attachée remarked, "Ah, why not take the mean of a hundred lunars?" You may be sure that the hundred lunars afforded a standing joke for many a day. I am still perplexed at the discrepancy between the Sun's longi tude correspo to g to the time of aphelion as given in the Naut Almanac, and that from the perihelion as given by Dr. Ball and all other writers on astronomy. No perturbation would account for it.-H. K. [44780.]-Stereoscope. - You can make a night-stoking is required. The joints to the pipes stereoscope to fold up and go into your pocket. are put together with elastic rings, and the pipes The base-board should be Sin. wide at one end, are connected immediately to the sockets of the 5in. wide at the other, and 7in. long; to the larger end hinge another board to carry the stereo slides, and to the narrow end hinge a frame carrying the will enable it to be held when in use.-W. J. lenses; a small handle, to screw into base-board, LANCASTER. [44794.]-Induction Coil.-The insulation will determine the quality of the coil; the better the. insulation the longer the secondary spark, and vice versa. Your coil should give a good thick in. spark if well insulated. If the insulation is bad, you might remedy it by taking off any cover you have made for it, and backing the whole of primary and secondary in melted paraffin in the oven for a day; then the probability is it would give a longer and better spark than now.-W. J. LANCASTER. [44753.]-Painting on Terra-Cotta. -To paint in oil-colours on the red or Leukos (creamy) ware, after sketching the design in pencil, as on cardboard or canvas, mix the oil-colours with body-colour like flake-white, but use Roberson's medium in place of much turpentine. Lay this on fairly thick, and let it dry for some hours; then tint and finish with the colours needed, without the flake white, but still use Roberson's medium. When quite dry and finished apply a slight coat of best copal varnish. Sable brushes are best. When quite dry, any pencil-marks can be rubbed out with indiarubber. If wanted to remove any spots of paint or mistakes, spirits of turpentine will do this. On Melas (black) ware the painting is to be [44803.]-Firegrate for Lancashire Boiler. treated exactly as painting on canvas, and needs, For a two-flued boiler 22ft. by 6ft., I should not therefore, no explanation, every stroke of the advise a greater length of firebars than 4ft., and not brush telling perfectly. Spots of paint or mis- less than 3ft. 6in. Firebars will do very well in takes can be rubbed off with a piece of wool one length up to 4ft. long, so you will have no as long as the colours are moist. To paint need for two lengths. The dead-plate should be with china colours on the red or Leukos for 10in. wide, and should rest on angle-iron brackets firing, use underglaze colours, and proceed inside the flue; if your flues have no brackets, you like painting on biscuit china. On enamelled can tap, say, four in. set-screws in, and let the terra-cotta for firing, use underglaze colours, dead-plate rest on them. The back-bearer will do and proceed as in ordinary china painting. made from a piece of 1in. square iron, either cast On the Melas (black) china colours are not appli- or wrought, and it should rest on brackets bolted cable, as the black colour does not stand firing. inside the flue; room must be left for expansion in The new black enamel is a charming novelty for this bearer, as well as in the firebars. It is a decoration with china colours. The using of china most reprehensible practice to allow this bearer to paints on a layer of white enamel laid over the rest on the flue, as they are apt to arch up with whole of the design, and which requires to be expansion if they do not damage the flue. I have "burnt-in" in a proper furnace, is, of the three known flues damaged through having middleways, the most "lasting," at the same time the bearers wedged across them. Top of dead-plate most expensive. There was an article on terra- should be 2in. below centre of flue, and 4ft. bars cotta ware in a recent number (I forget which) of should fall 2in. at back end. "Sunlight" has the Illustrated Carpenter and Builder which might given dimensions for a grate suitable for a boiler be interesting to "J." to read. Terra-cotta 30ft. by 7ft. 6in.-such, at any rate, is the usual means burnt or baked clay, and the art of using it practice here in Lancashire. In a 2ft. flue, you was cultivated at Rome in the time of the kings. could not keep a 7ft. grate covered with fuel at the Moreover, Mosaic history gives us instances of its back-end, and thus you would have a current of cultivation; in China the potteries have existed cold air passing into the flues through the bars for over 2,000 years, and in the Egyptian sarco-cooling the flues, thus wasting fuel or diminishing phagi and the Assyrian tablets we have proof that the evaporative power of the boiler.-SET. 3,000 years before Christ terra-cotta was used, although, as would be supposed at that remote period, the art of painting on it in oil, china, and water-colours, was not known.-MARGUERITE. [44764.]-Gyroscope.-I have had gyroscopes spinning ten to fifteen minutes easily. You must reduce friction to least possible unit, or it will not spin. The better way for you to hang wheel is to have two steel pivots screwed through ring, and working into two countersunk holes in centres of each end of axle. This will reduce friction very much, and you will find the gyroscope spin much longer than it does now with cone bearings.-W. J. LANCASTER. [44773.]-Faure's Condenser. You cannot overcharge this condenser; but by a little practice you will soon find how to tell when it is charged enough; then for dividing the current you can arrange the plates into sections, and have a shunt; but you don't suppose you are going to light half a dozen or a dozen lamps from one condenser. The Faure, at present, has done but little in lighting. I was altogether disappointed with it in Paris, after hearing and reading so much of the million foot-pounds.-W. J. LANCASTER. [44775.]-Feed-Water Heater.-To "SUNLIGHT."-Many thanks for replying to my query respecting the above, and forward further particulars as follows: We use a pair of vertical boilers, fitted with Field's tubes; distance from engine to boilers, 25ft.; exhaust pipe at present overhead, with a straight run of about 18ft. to shaft. We have a space of about 5 sq. ft. at dis posal near boilers, and plenty of head room. If you can recommend a heater of the annular form, a vertical one would suit us best, as space is valuable. The part we wish to heat with exhaust, after leaving heater, is within a few feet of boilers, and a floor above.-STOKER. [44777.] Telescopical. If your power of 80 gives a good clear disc when used on a firstmagnitude star, then the o.g. is not bad, but if there is a trace of the irradiation only in a lesser degree, then the o.g. is in fault. The o.g. should bear 200 easily. It is difficult to tell what a lens is without seeing it: if I had it here for five minutes, I could tell you all about it. As to the circles, 1 shall give the information you ask for, I have no doubt, before you want it. Also I shall fully describe various forms of stands. The wires on a micrometer diaphragm should be all soldered together; first drill as many small holes in the diaphragm on each side as you require wires, taking care to drill them true, then put one end of each wire through each hole, until all are in position, then solder the lot at once, put the other ends through the other holes on opposite side, draw all tight, and solder at once.-W. J. LANCASTER. [44807.]-Lighting.-One series of lights in a it feasible, would be a good one; as it is, it is an = 2K boiler, and circulate through an open-feed siphon fitted with a lid, so that there is no need for any cistern and supply-pipe. The fuel consumed is stated to be 161b. in 12 hours, and the apparatus is capable of heating, including the boiler itself, the equivalent of 80ft. of 4in. piping.-S. M. best way to heat the greenhouse would be to take [44832.]-Heating Small Greenhouse.-The out the kitchen boiler and bore a hole through it at the back, 1fin. from the bottom, to take in a piece of in. gas-pipe, then bore another hole the same size about 6in. or 7in. higher up the boiler, then screw the ends of the fin. pipe, which should be long enough to go through the wall into the greenhouse, then put on a check-nut and put the pipe through the hole in the boiler; put another nut on in the inside of the boiler, using red-lead, and a small piece of hemp; then screw all up tight, and fit the boiler into its place again, then you have the flow and return pipes, to which fit cast-iron pipes in the greenhouse. If J. Sharratt will send me a plan of the greenhouse, I will send him a sketch to work to. The water will circulate from the kitchen boiler through the pipes in the greenhouse; but there should be a stop-cock to prevent the heat becoming too great through the day, as night is the time when it is most wanted. There would have to be a small fire kept up through the night in frosty weather.-JOE BLAIN, Albertsquare, Carlisle. [44832.]-Heating Small Greenhouse.-If your kitchen boiler is one that is fed from a cistern at the side of the fireplace, you might utilise it by connecting it by means of in. or lin. iron or lead pipe with the cast-iron (2in. or 3in.) pipes in the greenhouse. If you use iron connecting-pipes each outside to keep them watertight, by means of they could be screwed into the boiler with a nut on a grummet and red-lead paint. One should go into the boiler at the top and be connected with the top line of pipes, called the flow, and the other should go in at the bottom and be connected with the bottom line of pipes, called the return. If lead pipes are used they could be connected with the boiler- and greenhouse-pipes by means of brass unions, to be purchased at any plumber's. The pipes should rise from the boiler to the furthest end about lin. to the yard, and in the bend at that point should be screwed a fin. gas-tap, and from it a small lead pipe should be carried up to the roof inside. This tap should always be open, to allow supplied from the top of the house, you would find any steam to escape. If your kitchen boiler is it more satisfactory to put up a small gas-boiler, as the pressure of the water would try the joints and prevent the vent-tap being kept open. The kitchen fire would, of course, be required to be kept in all night in frosty weather, and you would require taps on the connections between boiler and For pipes, to shut off the heat when not required.E. Boiler-Plates. [44831.] Strength of [44832.]-Heating Small Greenhouse.-I [44833.]-Logarithms.-The querist should procure "A Rudimentary Treatise on Logarithms," by Henry Law, C.E. (Weale, 59, High Holborn), price 2s. 6d. The appendix contained in above work has a table of every prime number from 2 to 1,000-also a table, by the aid of which the number answering to any logarithm can be found to six places.-ACONITE. Nickel would not answer for electrical contacts, [44839.]-Electrical Contact, Motor, &c.because it does oxidise when subjected continually to a high temperature. Now, for simple contacts, with a weak current circulating, nickel will answer, but it will not do for currents that would heat a contact. Froment's engine is altogether too clumsy for you to make or use; but there are several good motors. When in Paris I ordered several motors, and when I have them I will report as to best one for general purposes.-W. J. LANCASTER. [44840.]-Swan's Electric Light.-Swan's incandescent lamp is altogether unsuitable for working with Bunsen's cells. It is only satisfactory when used with a dynamo-machine; then |