J. V. H., of Va— It is really difficult for us to point out what is proper to claim that could be firmly established and retained. The process is patent-able—that is wherein it differs from the old ways ; this must be all clearly pointed out, explained, and claimed in the specification ; other specimens are required. The government fee is $30. S. S , of N. Y.-We will be happy to see you when you come down with your model, and will be able to form a more correct opinion respecting its qualities. D.S,of Leon—The Sci. Am will]be forwarded to your address for the term of your subscription ; subsequent subscriptions must invariably be paid in advance ; back numbers sent as per request. P. & S., of Pa —A gentle breeze exercises a pressure of about 083 of an ounce per square foot ; a high wind 1 1-2 lbs ; yeu can calculate from this what work you want done, and what amount of sail surface to use ; it would require no small amount of writing to furnish you with all the data for constructing wind-mills. We do not advise any person to erect a wind-mill where fuel is cheap ; get a steam engine. P. M. H , of D. C—You mistake the nature of radiation entirely ; it is merely an effort of chemical forces to restore equilbrium, and the common thermometer contradicts instead of eonfirming your theory ; the difficulties of using heat over and over again cannot be mechanical, if your theory is true; we cannot divine how you can entertain such an unscientific idea. E. H., of Iowa—In Vol. 3 of the Sci. Am. we published a hand-carriage for common roads ; it has never come into use. Your modification embraces nothing patentable, and weSfaise you not to spend time and money upon it. F. S,, of Mass.—An elflQjsfflagnetic passenger index was invented by OfSwrlfl, of England, some four years ago, and was at that time described in the London papers as a very beautiful invention, since that time we have heard nothing about it. N. C , of Ohio—We do not understand the meaning of the last part of your letter, J. W , of Md.—If your second tier of springs is above your city, the difficulty can be remedied by bringing your reservoir to that level where the lower springs can enter it. We see no other way to remedy the difficulty. When you can get water from a hill don't dig an Artesian well. J. Y-, of Mo.—Your plan is correct, excepting the string pieces, they should not be very thin. It is well understood that the embankment, if of sand, is the beat ; it would not answer to have plank roads in our city; the travel is too much for wood. For villages we think they are excellent. M. B. & Co., of Ohio—To obtain the information you want, copies of the specifications of the Wtr-stoves will have to bejobtained from theJPatent Of-ficej (and you will have to pay for them), as it is impossible to tell the patented points otherwise. J. S., of Ky.—It is utterly impossible for us to give the attention to your last letter, which you have requested. J. S., of N. H-—Spratt has a patent ; his conductor is a very good one. Any person can make a good conductor with, a piece of dry, well varnished wood. We do not know about Homer's. The best conductor 3 a copper rod, the thicker the better; if this is too expensive, get an iron rod, smooth, and of uniform thickness throughout. F. P. is here often. The M, M, P. is still in existence, and may yet do something. J. B. W., of N. J.—A B. Wilson, the inventor of the celebrated "Wilson Sewing Machine," residesat Watertown, Ct. OH. P. P., ofPhila—Your article on Water Wheels is too long j we do not wish to open our columns to a controversy upon tb# subect, we have had one already ; a statement of facts was all that was required ; Mr. 0. is well acquainted with the P. wheel and claims. W. B. C, of 111.—Scrapers suspended on an axis are old and well known; we see nothing new or patentable in yours. " J. B , of Pa.—You would see in a late number of our paper that the Atmospheric Telegraph is not new with you. R. A. S., of Mass.—We do not see what advantage your suggestion would be to Capt. Ericsson, about using a jet of steam with hot air j we consider the advantage would be to use all steam and no hot air. Money received on account of Patent Ofilce business for the week ending Saturday, May 7 :— J. S. V , of N. Y,, $30 j J. A.s of Ohio, $30 ; W. H., Jr., of Ohio, $55 ; S. C , of N. Y., $30 ; J. H , of N. H., $40 ; J. M , of Del, $30 j G. D., of Ohio, $3 ; E. R. F., Jr, N. Y., $50 Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday May 7 :— C. & S., of N. Y. (5 cases) ; F. D., of Va; J. M., of Del. ; G. W. F , of Ohio ; J. W. H., of R. I ; M. S- B., of N. Y. ; R. R. F., Jr., of N. Y. BAOK NUMBBBS AND VOLUMES—In reply to many-interrogatories as to what back numbers and volumes of the Scientific American can be furnished, we make the following statement'—Of Volumes 1, 2 3 and 4—none. Of Vol. 6, all but six numbers, price, in sheets, $1 ; bound, $175. Of Volume 6, all; price in sheets, $2; bound, $2,76. Of Vol. 7 all ; price in sheets, $2; bound, $2,75, Of Vol. 8, all the back numbers subsequent to No. 27, but none previous.