E. H. B., of N. Y.—We do not think a patent could be obtained for your invention. It has been proposed to make railway care and meat-safes—the formerwith their windows, and the latter with their entire sides— of canvas, and to keep the canvas constantly wet by properly arranged pipes, to produce evaporation, for the purpose of cooling the interior. W. C S., of Pa.—You can stain ivory black with a hot strong solution of logwood and copperas; and red With a hot solution of cochineal, cream of tartar, and a little alum, or what .*_ better, muriate of tin—use a very small quantity of the latter. Those who color ivory boil it in those liquors for a few minutes. Wash the ivory in soap and water, to remove any grease from its surface, before you stain it. See a recipe on page 94, Vol. 12, Sei. AM., for dyeing ivory red. C. E. S., of Minn. Ter.—We do not now remember any one who is engaged in making saw glimmers at Little Falls, N. Y. A line to the postmaster at that place would probably get you the information. Ii. Monsson, of Wilmington, N. C, wishes to purchase a hoisting machine for loading ships—one that will lift a hogshead of molas36fl. He desires to know the cost of a "beast" of this kind. 0. T. H., of N. Y.—You state that the mast distant cars of a train approaching Owego on the side hill appear to be the largest, whereas they should appear of a diminishing size, and ank an explanation of the phenomena, as you have found it L* not caused by the condition of the atmosphere. Without really seeing the train, we would be liable to give a wrong opinion of the cause ; but we think it must be due to reflected light, by which objects on the sides of mountains appear, in the distance, much larger, sometimes, than they really are, H. D. R, of N. Y.—You can probably get the carriage striping apparatus of Messrs. C. & C. by addressing them at Croton Falls, N. Y. J. S., of Va.—It is not very novel to place a cradle on castors, so that it may be removedeasilyfrom one room to another. B. P. B.,ofPa.—We thank you for the complimentary allusions to our journal in your letter, and are much pleased to learn that through it you have been able to surmount your business difficulties. J. B. F., of 111.—In the Hughes' telegraph, the type wheels of two apparatus, (the one at Philadelphia and the other at New York,) are so registered, as we understand it, that the one sends a letter in the intermediate of the other, and thus on the line with one wire two operators can be sending messages simultaneously from one city to the other. C. C. H., of Mich.—You havie inquired of us how gas burners were bored. The operations are simple, but require skill. They are drilled out in the inside in a lathe, to form the hollow chamber, and the two small angle holes are afterwards drilled by a forked drill. This is for fish-tail burners. The bat's wing burner, with a narrow slot in tho face, is first drilled in the same manner as that described for the fish-tail, then the slot is cut with a very fine saw. Proper tools are required for all these operations. B. F. S., of Cal.—The increasing or decreasing of the number of buckets in a water wheel or spokes in a carriage wheel is not the subject of a patent G. A. T., of N. Y.—You can procure dies for making stencilplatesfrom Smith & Hartmann, of 122&Fulton street, this city. T. G. S.,ofKy.—You will find articles on the preserving of timber on pages 317 and 395, Vol. XI, and pages 3, 93 and 336, Vol. XII, Sot AM. We understand that the process of preserving timber i s still carried on at Lowell, Mass., and at Northfield, Vt, on the Vermont Central Railroad, where you can witness the operations. We. have been informed that the treating of railroad timbers by Burnett's process affords a great Baving in railroad expenses. W. H. G., of Ohio.—There is no substance which you can interpose between a piece of soft iron and a permanent magnet to "stop" the attraction. The attraction of the magnet is inversely according to the square of the distance. Dry air or a plate of glass are about the best non-conductors known. U. T., of N. Y.—The best substance you can employ to preserve wood exposed to water in a well is "pitch." Put it on the wood as hot as possible, and allow it to dryperfectly beforeyouput it into the water. Jf you use the cbloride of zinc or the sulphate of copper to impregnate the wood, long exposure in the water will tend to decompose the metallic salts, and thus injure the water. W. M. S- of N. Y.—We have heard that the railway tunnel through Mount Cenis was suspended on account of the difficulty of supplying it with fresh air, but we doubt the correctness of such reports, because many coal mines with subterranean passages of much greater length are supplied with fresh air by well knownmeans, which may be applied to the railway tunnel. E. C. M., of N. Y.—We never buy or sell patents or accept an interest in any invention on any terms whatever, therefore your request c nnot be complied with. - A. S. Langley, of Nashville, Tenn., desires to correspond with manufacturers of bakers' ovens and cracker machinery. He also wishes to purchase a good spoke machine. W. W., of Cal.—Your plan of placing a screw in front of the plowshare to be kept revolving to prevent the stubble or grass collecting on the share is not new. A model presenting essentially the same feature has been # in our office for some time. Your mode of steaming j squirrels in their holes would not be patentable. 'Y F- H., oflll.—The first 26 numbers of Vol. XII we A have not got to supply you. We can send you all the yfek back numbers of the present volume. F. P. C, of N. C—We do not know of any machine for the separation of gold from other ores by washing that will do without constant watching, and we are inclined to think that such a one is wanted. Why do you not try and invent one ? J. C, of N. Y.—Those French timepieces to which you refer cannot be found for salejin this city. B. R. B., of Pa.—The plan you describe for raising vessels or other objects is not new. The enclosing of an india-rubber bag within ribs of metal to inflate under the waterafterbeing attached to the object to be raised is an idea submitted to us very frequently. E. T. B., of Ct—Your egg-beater, we think, possesses patentable novelty. H. M. H,, of N. Y.—Feldspar is to be found in Thomson quarry, up about 196th street, on this island. We do not know the price of it. M. J. II., of N. Y.—There are dams built with an inclined instead of a perpendicular face. These appear to embrace the same principle as that you have described to prevent vibrations. We do not think a patent could be obtained for your method. Money received at the Scientific American Office on account of Patent Office business, for the week ending Saturday, March 20,1868:— D. II., of N. Y., $55; G. P. J., of Iowa, $20 ; A. 0., of Canada, $30 ; J. B. McC, of Ky., $25 ; J. H. F., of Vt, $20 ; J. M , of Ga., $125 ; J. T., of N. Y., $55 ; W. S., of Wis., $25 ; J. M. S., of Cal., $15 ; C. & B., of N. Y., $10 ; G. S. R., of Ohio, $30 : G. H. K, of N. J., $30; P. & H., of Conn., $30 ; W. R, Jr., of Mass., $15 ; T. & S., of Pa., $12; B. A. B., of N. Y., $35; J. T. R, of Conn., $60 ; G. N., of Ohio, $90 ; H. H. P., of N. Y., $25; C. C., of R.L,$30; C. E. &J. N. G.. of Pa., $27; W. G.ofN. Y.,$30; F. & L. A. C, ofN. Y., $30 ; D. M. L., of Pa-, $25 ; R C. Van D., of Ohio, $25; E. A. C.,ofVt, $10; G. W. D.,of Iowa, $35; L. L. C, of Conn., $30; J. T. R R-, of N. Y.,$52 ; F. Y., of Ky., $30 ; J. A. St J., of Wis., $30 ; I. R L., of Ind., $25 ; T. S. R., of Ga.,$35 ; B. & W., of Pa., $30; S. T., of Mich., $20 ; L. B. S., of N. Y., $10 ; D. J. W., of Ohio, $30 ; J. Md., of N. Y., $25 ; J. T., of N. J., $25. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday, March 20,1858 :— J. T., of N. J. ; T. &. a, of Pa. ; R &F., of N. J. ; W.S.,ofWis.; J. De R, of Ohio; G. P. J., of Iowa; T. S. R of Ga ; T. F., of N. Y. ; H. & B.. ofN. Y. ; J. R L., of Ind. ; H. H. P., of N. Y. ; D. M. L., of Pa. R C. Van D., of Ohio ; C. E. & J. N. G., of Pa
This article was originally published with the title "Correspondents"