424 A MR. SPILSBURY'S PATENT METHOD OF TANNING. is placed, then a second hide is laid above it, and a third frame is put, above that. The three frames are arranged so that the metal loops of each shall be opposite those of others; screw bolts are then put through those loops, and screwed up sufficiently tight to prevent any liquor from passing between the frames and the hides. The whole is then set up edgeways, and there being two short pipes, furnished with cocks, in the upper edge of the middle frame, a pipe, in which there is also a cock, that descends from a cistern holding tan liquor, is fastened to one of these by a union joint; and another cock being placed near the bottom, in the same frame, to let off the liquor when required, completes the whole apparatus. the lower cock, and the frames separated from the tan pipe and from each other; and the hides being removed, and having their edges pared off, which were nipped or compressed between the frames, are then to be dried and finished in the usual manner. Nothing further is stated in the specification respecting the time which this process will require, but that it must depend entirely on the nature of the hides or skins. The New Repertory of Inventions has the following remarks on the value of this process: "This method of tanning has attracted much attention; and it is reported that hides of that thickness, to require a year for tanning in the common method, can he finished in this in six weeks; and that some skins can be tanned by it in eight or nine days; it is also said, that a very large sum of money has been offered for the patent right. The cock at the top, that communicates with the tan cistern, being opened, and the other near to it being also opened, while that at the bottom is shut, the tan liquor will run down between the hides, driving out the air at the other open cock; "The theory of the process apwhich, as soon as any liquor ap- pears to promise well for quick perpears in it, being shut, the tan li formance, but on these occasions it quor will then distend the hides, and is necessary to attend to facts; and press outwards, with a force pro- we have been informed by some genportional to the height which the tan tlemen in the trade, that the hides cistern is elevated above the frames. are not tanned evenly by this meThe consequence of which pressure thod, but leave spots less acted on will be, that the tan liquor will ouse by the liquor than the rest; and that through the pores of the hides, ap- leather made in this way is not so pearing at the outside like dew; and durable as the common sort. by thus bringing fresh portions to act continually on them, will, in the opinion of the patentee, cause them to be tanned much more speedily than happens in the common method, in which the hides lie in the liquor, after it has ceased to operate on them, and are only passed into fresh liquor at intervals by a tedious manual operation. The frames are to be made of wood or copper, and if iron should be used for them, it must be well painted, to prevent its making the hides black. In some cases, two skins or hides be put at each side of the mid may 1 "The quantity of the hides that must be pared off when they come out of the frames, must certainly diminish the value of the process, and especially when oblong-square frames (such as are represented in the figures of the specification) are used, which, not being of the natural shape of the hides, must cause more waste; which must be worth consideration, even though the parts to be cut away are the least valuable of the hides, vai o It must, however, be considered that this method of tanning is still in its infancy, and that it will be protime, so as to diremove dle frame; and when the whole are bably meand "well tanned, the tan cock is to be closed, the liquor is to be run off at 16919 minish others, of these objections made to it. ད་པ་འབས་ sida bna,ɔsjonq, of shami 19 padt not or den d INSTRUCTION FOR MECHANICS AT PARIS. a rope, made of a species of long grass, and which floats near the surface, has only to move his canoe where he perceives there is a rocky bottom; this done, he throws the rope out, so as to form a tolerably large circle; and such is the timid nature of the fish, that, instead of rushing out, it never attempts to pass this imaginary barrier, which acts as a talisman, but instantly de scends, and endeavours to conceal itself under the rocks. Having waited a few moments till the charm has taken effect, the fisherman plunges downwards, and not unfrequently returns with four or five fish, weighing from two to six pounds each. As they seldom find more than the heads concealed, there is the less difficulty in bringing forth their rich prizes; and when the harvest is good, the divers are so dexterous, that they have a method of securing three or four fish under each arm, beside what they can take in their hands. The fish greatly resembles the John Dory. 431 freezing point of mercury, if the experiments were made at a temperature a little under 32o. POWER REQUIRED FOR DIFFERENT VELOCITIES OF STEAM-BOATS. We extract the following Table from a valuable paper on Steamboats, by Mr. Tredgold, in the last Number of Professor Jamieson's Edinburgh Philosophical Journal. The immense increase of power which appears to be necessary to obtain a small increase of velocity is very remarkable, and must have a great influence in inducing a preference of engines of a moderate size. The calculation applies to still water. Miles per hour. 3.... Horses' power. 51 4... 13 5. 25 6. 43 7.. 69 102 REFRIGERATING SALT. If we mix 57 parts of muriate of potash with 32 of muriate of ammonia, and 10 of nitrate of potash, a refrigerating salt will be produced. This salt, put into four parts of water, and quickly agitated, will make the thermometer descend from 20° to 5o below zero in Reaumur's thermometer. COLD PRODUCED BY THE COMBINA TION OF METALS. According to M. Dobereiner, the fusible metal consists of one atom of lead, one of tin, and two of bismuth; and it becomes fluid when exposed to a heat of 210°. If the fusible metal, formed of 118 grains of filings of tin, 207 grains of filings of lead, and 286 grains of pulverised bismuth, be incorporated in a dish of calendered paper, with 1616 grains of mercury, the temperature will instantly sink from 650 to 140. M. Dobereiner thinks that it might sink so low as the 10.. INSTRUCTION FOR MECHANICS The celebrated Baron Charles Dupin, of the Institute, has undertaken to give instructions to the industrious classes in geometry and in mechanics, as applied to the arts. His instruction extends to the great manufactures, as well as to the most ordinary and common arts of life, and even to the fine arts. The architect, the carpenter, the mason, the sculptor, the painter, and the engraver, each require a knowledge of certain geometrical or mechanical principles: M. Dupin supplies them with this knowledge. The knowledge he teaches is necessary to all mechanics, and artists who have any thing to do with mechanics. In some cities of France some learned Professors have hastened to follow M. Dupin's example, and others propose to follow it.-French Paper. The glass chimneys which are now in such general use, not only for oil lamps, but also for the burners of oil and coal gas, very frequently burst, owing sometimes to knots in the glass, when it is imperfectly annealed, but more frequently to an inequality of thickness at the lower end, which prevents the glass from expanding uniformly when heated. M. Cadet de Vaux informs us that, when the evil arises from the latter cause, it may be cured by making a cut with a diamond in the bottom of the tube. He states, that in an establishment where six lamps are lighted every day, and where this precaution was taken, there was not a single glass broken for nine years. ANSWERS TO INQUIRIES. No. 147.-COLOURING BRICKS. SIRI.send. the following you receipt for colouring Tiles :-. Take one ounce of red lead to three ounces of manganese; get some strong clay, mix it with clean water until it is as thick as cream; pass it through a very fine sieve, then mix it with the lead and manganese. Let your tiles be dry; then pour it over them, and set them to dry. Do not let them touch each other in the setting, and keep them free from dust as much as possible in the kiln. I have only made one trial of this method, but it answered very well. To make your bricks and tiles of one colour, mix all the different sorts of clay well together. I am, Sir, Colston, Near Nottingham. of gum mastic, and half a pint of turpentine varnish (which may be got for less expense at the colourshops than it can be made for, except in large quantities); put the above in a tin can, keep it in a very warm place, frequently shaking it, until dissolved; strain it, and keep it for use. Should you find it harder you wish, you may add a little more turpentine varnish than HENRY HOPE. ནི་སྒྲ་ལསྤྲུགས NOTICES ΤΟ CORRESPONDENTS. understand entirely the "A Real Friend," and "the circle" of friends he represents, seem to misprinciple on which our publication is conducted. Were we to admit nothing but what is unquestionably correct and good," the Mechanics' Magazine would be converted into a mere repository of wellknown doctrines and precepts, instead of continuing, as it has heretofore done with so much approbation, to be the vehicle of every thing in the shape of original and ingenious speculation. Conimunications received from-Experimentum-Crucis-A Mechanic-M. Welch-J. C. E.-W. S.-W.. B.—Mr. Thomas-F. J-k-n-Jack Long—T. S. -A. B.-J. O.—W. C.—B. P. C.—Samoht-G. S. Advertisements for the Covers of the Monthly Parts must be sent to the Publishers before the 20th day of euch Month. NO. 137.-VIOLIN VARNISH. Take half a gallon of rectified spirits of wine, to which put six ounces Communications (post paid) to be addressed to "the Editor, at the Publishers, KNIGHT and LACEY, 55, Paternoster-row, London. Printed by MILLS, JOWETT, and MILLS (late BENSLEY,) Bolt-court, Fleet-street. SECRETS IN SELLING-SIR H. DAVY'S COPPER SHEATHING. right-angled triangle, DAH, of which DA (the hypothenuse) will be the greater side; and, therefore, DH is less than DA, and within the circumference; and (by Prop. 2, Book .) AE cuts the circumference in two places. Your Correspondent (or dents) will not need to be reminded, that a mathematical point or line is not such as to be seen by the naked eye, nor even by the best microscopes. The points and lines in a diagram are seen, but they are merely a guide to the inward or mental view. In such questions as the above, we must first draw lines at perceptible distances; and if we want to draw conclusions from imperceptible distances, we must carry on the operation mentally, from the facts deduced at perceptible distances. I am, Sir, R. H. [We have also received answers ad Discipulos from Amicus, Acute Angle, Napier, B., J.P.G., F.O.M., and Zero, one or more of which we shall (probably) give in our next.EDIT.] SECRETS IN SELLING. : SIR,--I am afraid C. M. will still find himself a little in the mist, notwith standing the ingenious solution given by F. O. M., page 381, for how he is to find the value of 0 from the two heights of the barometer? I shall propose the following question to be solved from F. O. M.'s formula:Suppose a cubic foot of cork exactly balances 241 ounces avoirdupois of lead, when the barometer stands at 289, what will be the weight of the same piece of cork when the barometer stands at 310, the temperature of the air in both cases being 55o ? I am, Sir, Yours respectfully, G-S-. P.S. Mr. F. O. M. does not show what correction should be made on account of difference of temperature. 427 SIR H. DAVY'S COPPER SHEATHING. The following paragraph from the Plymouth Journal has, during the past month, gone the round of all the newspapers: "Failure of Sir H. DAVY's Plan for the Protection of Ships' Bottoms. commended by Sir H. Davy, to preThe plan some time since rebottoms, and which was adopted by vent the oxidation of copper on ships' Government, with a laudable zeal for the interest of science, has not been found to produce the expected benefits. In the instance of one of his Majesty's ships, which was fitted four years ago upon Sir H. Davy's plan, and which is now undergoing repair in this dock-yard, it appears iron has indeed prevented the oxithat the galvanic influence of the dation of the copper, but the bottom of the ship is found, as in the case of wood-sheathing, to be foul with weeds and barnacles, to provide against which, copper bottoms were originally adopted. We understand that orders have been received to discontinue the fitting of his Majesty's ships upon Sir Humphry Davy's principle." We deferred copying this (apparently exaggerated) statement into our publication, until we should see what answer or explanation it would draw forth from the learned President of the Royal Society, or his friends. In the Annals of Philosophy for the present month (October), Mr. Children has given the explanation for which we waited. It appears from this, that Government have not abandoned Sir H. Davy's plan altogether; that the application of his protectors is merely suspended for sea-going ships; and that it is ordered to be applied to all ships in good condition in ordinary (the Royal Sovereign, for instance), as also to stationary ships, such as sheer-hulks, receiving-ships, &c.— Mr. Children adds the following remarks, in the spirit of which we fully concur : It is not for us to question the propriety of the measures adopted by the Lords Commissioners of the Admiralty, though we cannot help |