J. P. C, of N. Y.—The same plan of propulsion by pistons, forced into a water chamber against the water at the stern of a vessel, has been proposed to us before, but it is not new; it is illustrated in the London Mechanics' Magazine f orl845. L. A S., of Pa.—We fully concurin your arrangement with the Commissioner. S. C, of N. Y.—We think your model illustrates a new invention, as far as the securing the spokes to the hub is concerned, but the application of the invention to railroad purposes, or the using of double axles upon railroad trucks, is impracticable as you have them arranged. H. S. W,, of Miss.—It is quite true, as you say, respecting the pressure of the atmosphere on the cannon or musket; this amounts to 15 lbs. on the square inch, and acts upon the gun by crushingf orce in proportion to the size of the cannon and the smallness of aperture behind the shot; cannons and fire-arms are made strong to resist the whole expansive and contractive forces. It would never do to lose time on a field of battle, to extract the air by a pump ; the time required is a great deal. We have known of a fowling piece made with a large vacuum chamber attached, for still shooting, in order to prevent noise by the discharge. G. C, Jr., of Mass.—You can obtain a pamphlet of Geo. Carvill, 86 Cedar St., edited by Sereno Newton, which will instruct you in regard to setting out gear. Price, we think, is 50 cents. J. M M., of Mich.- A locomotive, with its tender loaded, all weighing no more than 20 tons, ean be built to work up to 60 horse power. Ask the locomotive machinist of any railroad and he will tell you this can be done. You know that steam plows have been used ; and you are no doubt able to judge of its economy ; if it would be profitable to you we advise you to go on. D. B. C, of N. Y.—We have not seen such an instrument exactly, although there is a vertical plummet, with an index and pointer, Illustrated in Vol. 1, Sci. Am. The spirit level is not attached. You have not fully explained its use, application, andthe necessity for the sector teeth. L. S., of Va.—We inform you, on the authority of Lieut. Maury, that the Trade Winds cannot be accounted for by the earth's rotation. Without the earth'srotation we assuredly would not have trade winds; and without it we would not have dew on the grass, but the dew is not caused by the earth's rotation. P. O., of Me.—You are mistaken in regard to the cause of the pain experienced by persons who ascend in balloons. The air of the upper regions is more rarefied than that on the earth; and the air inside their bodies (seeking to become of the same rarity) bursts through their eyes aad ears, producing intense pain. C. R., of Pa.—Oxygen gas supports combustion. Blowing lighted tinder carries oxygen to it and quickens it, in the same way as a pair of bellows quickens a dull fire. H. A., of Mass.—Your inquiries concerning Ray's Prizes are fully answered on another page. D. C. T., of N. Y.—The specification and one drawing of your Alarm were sent you on the 8th inst. W. F., of Tenn.—We shall give your order immediate attention. $500 received, A. B., of Miss. —We have carefully examined the sketches of your Lathe and findnothing new. Lathes are made in this city embracing all of your improvements. L. A. H., of Va.—Ericsson's Caloric Engines are not as yet fully tested, and it will be several months before a satisfactory answer ca,u be giyen to your inquiries. Like all other untried inventions, it is uncertain what its practical value may be. J. N. F., of Va.—The engine recently advertised by us has been disposed of. S. T.3 of N. Y.—We cannot give you a decision in regard to the point of infringement; we are not in the habit of giving opinions in this respect. S. F. W., of Miss.—The first steamboat that was ever used, was launched on the Hudson in 1807. B. M. B., of Ga.—The number of miles of railroad in the United States is over 12,000, costing $300,000,000. C. T.. of Me.—We have never seen the description of the machine you mention, A. Y. N., of S. C—Lord Bosse's Telescope is fixed in a building, on his estate in Ireland, but it is not the largest, being excelled by Mr. Craig's, near London. W. N., of Ala.—The best plate glass is imported from France. A. V. N., of Mass.—Chipping is always done by hand; we are aware that thare is a machine for chipping off roughly, used at a factory on the East Ri-ver, but for fine work it is inapplicable. A. W., of Texas—Mercury is found in several part* of the globe. Money received on account of Patent Office business for the week ending Saturday. NOT. 6:— J. E., of K. L, $15; O. L. R., of N. H., $51: C.P. B.ofR.I, $30; A.A. D., of Geo., $40; A. J. W., of N. Y., $50 ; J. B. A., of Ct, $30 ; H. B., of O., $20; M. H. C, of Pa., $20, S. B., of L. I., $55 ; W. D. W., of N. C, $30 ; G. S., of L. L, $62. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office daring the week ending Saturday, NOT. 6: J. E., of R.I.; O. L. R., of N. H.; R. S, of N. T? H. ,B., of O.; A. J. W., of N. Y.; G. S., of L.I,; i M. C, of Pa.
This article was originally published with the title "To Correspondents"