DENISON'S MACHINE FOR STRETCHING WOVEN FABRICS. [Registered under the Act for the Protection of Articles of Utility. Samuel Denison, of Harwood-street, Leeds, Proprietor.] FIG. 1 of the prefixed engravings is a plan of this machine, and fig. 2 is a sectional elevation on the line ab of fig. 1. AA is the framework; BB, two drums, which are mounted in such manner on the spindles, CC, as that they may be made to travel from or towards the centre of the machine, as may be required. DD are two screws, by which this to-andfro movement is effected; the screws are passed through the arms of the drums, BB, and work in two fixed arms, EE. FF are wheels for giving motion to the drums; their bearings are affixed to the table, G, which is slid backwards and forwards upon the framework, AA, by means of the hand-screw, H. I is a breastwork of iron bars, over which the fabric to be stretched passes to the drums, BB, to the peripheries of which last the fabric is attached by a number of small pins projecting from their surface, which take into the selvages of the cloth. The degree of stretching to be given to the cloth is regulated by a hand-wheel, H. KK are guides, acted upon by the handwheel and screw, L; M is a hand-wheel and screw, which are attached by a swivel coupling to the end of the screw, L, and move both the screw, L, and the guides at the same time. N is one of a pair of revolving brushes, the office of which is to press the fabric on to the pins on the drums, BB. (These brushes stand above the guides, K, and are only shown in fig. 2.) 00 are strippers which liberate the fabric from the pins, and pass it on to the cutter, P, which is worked by the gearing, RR. S is a steam pipe (having arms of different lengths), to steam the goods while passing over the drums. COMPARATIVE POWERS OF DIFFERENT GALVANIC BATTERIES-HOW MAY HAY BE ARTIFICIALLY DRIED? Sir,-Your correspondent, of Carmarthen, asks-Why Grove's battery is superior to Daniell's, and Smee's inferior to either? &c. As no one has replied to him, I venture to send my humble opinion on the matter. Grove's battery is excited by a highly oxidating fluid, nearly pure acid, and the hydro gen liberated is removed and absorbed by the nitric acid: in Daniell's battery, the exciting fluid is not so strong as in Grove's, but the hydrogen liberated is instantly absorbed by the oxygen of the oxide of copper, the pure metal being deposited on the negative plate. This removal of the hydrogen is so important an element in the efficient action of a galvanic battery, that, although Smee's contains a more highly negative metal than Daniell's, yet as no provision is made in it for the absorption of the hydrogen, the working power of Smee's is inferior to that of Daniell's. As to the anomalous position of iron as a negative plate, and its superiority over copper in this capacity, if your correspondent will refer to the Philosophical Magazine for 1840, 1841, or 1842 (I forget which), he will find the matter elucidated by his fellow-countryman, Mr. Martyn Roberts, who was the first to discover this peculiarity of iron in the battery. His paper on the subject is an answer to Professor Poggendorf, of Berlin. But there is a condition of iron, not yet explained by Roberts, which is its negative character when not associated with other metals, as a galvanic pair, after the iron has been for a short time plunged into nitric acid; but this property is, I believe, easily to be accounted for. "May I, in return for my answer, ask a question. I live not very far from the Arctic Circle, and our summer is consequently short and desperately wet. Can any of your correspondents tell me a cheap way of drying a field of hay by artificial heat. We should be able to dry, at least, some five tons a day. I am, Sir, Your constant reader, 0. CONTINENTAL METHOD OF CALCULATING AND SETTING OUT RAILWAY CURVES. Sir,-The following method of calculating and setting out railway curves may perhaps be found useful by some of your readers. I have used it a great deal myself, and have always found it the most correct, as well as quickest of all other methods, more especially, however, for permanently setting out the line of railway. It is used, I believe, by the engineers of the Ponts et Chaussées in France and Belgium, and on the Continent generally. In the calculations I have employed logarithms, but should any of your readers be unacquainted with their use, the same operations may be performed by common arithmetic. Now, in commencing the tangent lines, AB and BC, should be run until they intersect at B, and the angle, ABC, taken correctly with the instrument, which angle, we will suppose for the sake of example, to measure 160°, and we will also suppose the radius of the curve in this instance to be 100 chains; it is then required to calculate and set a curve, the pegs of which, may be of equal or unequal distances from each other. The value of the angle, ADC will be 180°-160° -20°; then by referring to the accompanying diagram, let AD and CD be drawn at right angles to AB and BC, divide the arc, AKC, or half the arc AK into any number of equal or unequal parts (in the diagram they are equal), and let A, g, h, i, j, k, be the pegs of the curve; join g, h, i, j, k to D; also draw fg, eh, di, cj, bk, at right angles to the tangent, AB; draw also lg, mh, ni, o j, p k, parallel to AB, then will Ab-pk and Ac=oj, and also A p=bk, and also Ao cj, and so on. We proceed then to find the length of the curve which will be 1.5429074=34·9066 chains, say 34.90=AKC. Having the length of the curve, we determine the number and distance of the pegs from each other. In this example we have supposed 10 pegs and the length of half =3.49 chains distance between the pegs; also the the arc being 34.90 17.45 2 = 5 angle, ADC, being 20°, we have 20° = 10° 10°, the angle of half the curve, and. =2° 5 :: the angle of the distances between the pegs. We then proceed to find the length of the tangent lines, AB and BC, which will be as 10,000,000: rad. of 100 chains: natural tangent of angle 10°-17.632 chains, or by logarithms, we have rad. of 100 chains 2.0000000. Log. tangent of <10°=9-2463188 11.2463188 - Rad.10.0000000 1.2463188-17·632=AB. We next find the length of Aƒ, Ae, Ad, Ac and Ab, by the same operations for the length of the tangent, only substituting the line of the angle for the tangent; thus for lg. and so on for Ac and Ab. Having now computed the various lengths on the tangent, we proceed to calculate the lengths of fg, eh, di, e j, bk, by the same rule as before; substituting, however, the cosine for the line of the different angles, and substracting the result from the radius of the curve. and so on for cj and b k, which will complete the offset from the tangent. Should the point B, be inaccessible, a parallel to AB may be run; as for instance, the line pk produced to q, and the angle taken. If the point A is fixed and the radius of the curve unknown, let the operation for finding the length of the tangent be reversed, we will then have, Log. tangent < 10°=1·2463188 - Rad. 10'0000000 11.2463188 -Log. of 17.632=9.2463188 2:0000000-Rad. of curve = 100 chains. In conclusion, I have to observe, that the only lines required on the ground are the full lines drawn in the diagram, and not the dotted ones. steam to supply fresh water for the ship's crew, affords an example of his attention to the collateral uses to which an invention may be applied; the idea of fixing the wheels in the middle of the vessel, were it realized, would even at the present day be productive of considerable advantage, in war steamers particularly, by placing the locomotive apparatus out of danger from shot, and in regard to all vessels, the enabling them to make use of the whole apparatus, though they should heel so considerably as to raise one wheel as at present out of water. Bentham was at that period studying naval concerns, as a master shipwright's apprentice, in Chatham Dock-yard, where though little of his time was employed in actual work, yet a Royal dock.yard was not the place for bringing such a project as steam navigation to maturity; besides that, his views tending to the improvement of naval concerns generally, he was led rather to seek an increase of his acquirements by severe study, than in any way to bring forward inventions of his own to public notice. Fragment of a project for Steam Navigation in the year 1774, by Samuel, subsequently Brigadier-General Sir Samuel Bentham, K.I.G. Two cylinders at least to each wheel. Pistons each by rising and falling, to turn the wheel by a crank. Length of the crank may be commensurate to the power and velocity required. There may be some apparatus to connect the two wheels, or in the lower part of the cylinders to each wheel there may be an exact fitted plug. If the plugs of the cylinders of one wheel be unstopped, that wheel would stand still, so may it be guided. The velocity may be increased by increasing the force of the fire by registers in the furnace. The upper part of the cylinders may be fitted into a trough of water, then a hole may be made in it, at which when the piston is lifted up, the water will run in to condense the vapour, then the piston will fall; and so on. The wheels might have leaves, and be put to a boat. Such boat should be as little as possible above the water, to be affected little by the wind. For large barges the wheels might be in the middle of the boat, built like two halves at a little distance from each other; the wheels then would not be in the way when coming alongside other boats; and perhaps the water would be smoother between the halves than on the outside. Query. Is there any better way of producing a circular motion from a vibrating one than by a crank? Probably none more simple. The piston may terminate upwards in a cogged bar or rack; this rack may turn a wheel when lifted up, which wheel may be disengaged from its axis when the rack falls. There may be a small paul to the wheel, which may catch in the axis; then this paul, when the wheel is turned one way, will catch hold of the axis, and turn it with it. If sails were set, the wind might assist either B or C* There may be a hollow tube in the rack, the upper end of which may be stopped by a plug: this plug may be opened when the rack is lifted up to its height, on which the steam would rush out at that hole, and the piston would fall; at the end of its fall, this plug might be made to shut, consequently the piston would rise again, and so on. The steam when it rushes out might pass down into a receiver at the bottom or side of the vessel, so as to be kept always cool by the contiguous water. By this means a quantity of fresh water would be made continually, so that though it would be necessary to take a quantity of coals, it would not be to take water. This receiver, indeed, would take up some room, but not more perhaps than twoquarter casks. MR. TATE'S DEMI-SEMI-EUCLID. Sir,-The reviewer of Tate's DemiSemi-Euclid appears to have been misled relative to the extent of geometrical knowledge required by the Committee of Council on Education, in order to entitle examinands to certificates; and as the remarks made by him are calculated to depre ciate, in public estimation, the value of such certificates, I trust you will permit me to correct this mistake. If Mr. Tate asserts in his preface, that three books of Euclid are all that the Committee of Council require, It would seem that these letters refer to some sketch made on missing pages. |