J. C. S., of N, Y.—You appear to have hit on the Ericsson propeller; the single propeller, with an in creasing pitch in the blades, has been the most suc cessful : it is more simple and can be made cheap er ; we prefer it. Sir G. C.'s ideas are to be found in the " London Mechanic's Magazine," in the dis-cuasion of the Stirling Air Engine, 1846. N. R.M. & Co., N.Y.—Your water-cock will work well enough, if the column of feed water is of great er weight than the pressure of steam on the water in the boiler; if not, the water in the boiler would be forced up the pipe. F. C of Mich.—Your torpedo would no doubt be of great benefit, in cases of danger, if constructed as you propose , but as we do not know the plan, you will readily judge that we cannot Bay more about it, A. M, S., of Ind.—You should write Messrs. Doug lass, of Middletown, Conn., for such information as you solicit of us. Those odd back numbers we have not. Subscribers at Mount Morris, III.—Your first letter came duly to hand with funds, but the name of the State was omitted both on the letter and on the en velope which covered it, so we knew not where to address the papers. Very many of our correspon dents are too careless about mentioning the name of the State from whence they hail; by being more particular in this respect they will save themselves, as well as us, much trouble sometimes. J. E. B., of N.—We have received yours but do not understand the case, because you have not ex plained it, and your letter does not clear up the cir cumstances ; a plain and clear statement of the cir cumstances is the thing wanted in connection with the elucidation of the power of the engines and speed of the screw. Write cautiously and clearly. A. J. M. D., of Geo.—Capt. Ericsson first built a stationary hot-air engine. You have got the re ceipt for glue by this time. The amount for the two patents would be about $1100. H. D., of ?. ?.—Alum water will taa your white skins j be sure and get the grease out of them ; it requires practice to do so correctly. H. M. S., of ?. ?.—We do not see any novelty in your arrangement of windmill, and feel sure no pa tent can be obtained. P. O.j of Ky—We keep Concentric Lathes con stantly on hand, price $25 : also a very compact mortising machine for $20 you can order at any time. S.P-, of Pa.—We are not acquainted with any better substance for smoothing the spokes than what you are using, J. S- D., of Tenn,—There is nothing new or paten-table in your alleged improvement in brakes ; the principle is good bttt not flew. :J. M., of Pa.—G. W. Terry, of New Haven, Ct., can furnish you with information about works on distilling and alcohol. J. V- S,, of Ohio,—We see nothing new or patenta-ble in your device for feeding water to boilers. * 0, F. M,, of C. W—No person can instruct you how to make malleable iron, you must learn the trade like any other profession, L. B. C, of S. C—We feel greatly obliged to you for the fine list of subscribers received from you, and regret that we are unable to furnish your club with the back numbers. J. W. G-, of Ind-—The edition of Minnifie's Draw ing Book, now publishing in numbers, contains the same matter as the work originally published ; price in numbers 25cts. each ; bound, $3, exclusive of pos tage, which is about 30cts. J. C, ofN. H.—You will find several good receipts for making ink, blaok, blue, and red, in Vol. 7, Sci. Am., page 91. D. G. S., of Pa.—Your paddle-wheel is too com plicated to be of any practical benefit if put into use. A. P., of N. J.—Your description is too concise to give a decided opinion upon the subject. E. C. ? , ofN. Y.—We do not knowwhere Jeffries' Marine Glue is obtainable, perhaps the following recipe will be a substitute : cautchouc, 15 grs.; chlo roform, 2 oz. ; mastic, 1-2 oz.; dissolve the two first ingredients, then add the mastic, and leave it to macerate for a week. Another glue or cement is made by mixing a handful of quicklime, with four ounces of linseed oil, washed, and boiled to a good thickness, and kept in the shade on tin plates to dry; it is afterwards rendered fit for use by boiling it over a fire. L ? , of N. Y.—The magnet will not attach it self to the wheels. Blast Pipe—Who can tell us what was the cause of the bursting of the blast pipe at the Crane Iron Works, Pa , recently ? E. A. F., of S. C.—We have received yours, and think as you do on the subject. J. B. C , of Tenn.—Yours has come to hand and will receive attention. Money received on account of Patent Office busi ness for the week ending Saturday, March 26 :— J. A , of Ct, $25 ; H. R,, of N, J., $30 ; T. F., of Ct., $20 j J. H, B., of Ct, $30 ; J. B,, of N. Y., $20 ; B. H. O-, ofN. Y., $30 ; A. C, ofCt., $25 ; F. O. D., of Pa., $20; R. C W.,ofO.,$55 ; J. M., of Del, $25; H. B., of Ct., $30 ; N, N. T., of N. Y., $30 ; H. C. ? , of N- Y., $30 ; W. ? , of N. Y.', $30 ; R. S., of N. Jo $30, Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday March 26 :— J. ?., of Ct.; B. J., of N. Y,; A. L. MCJ., of Ohio; & A. & J, G., of R. I.; T. J ?.,of Ohio; A, C, of Ct. ; S W. & G., and R M. D., of Mass.; J. T., of v 111.; J.B., of R. I.; R.S., of N.J.