CHEAP POSTAGE.—The postage on the Scientific American, to subscribers residing within the State of New York, will be but 13 cts. per annum henceforth, instead of 13 cents per quarter as formerly, and will be delivered at the most remote parts of the United States for 26 cts. per annum, whereas the postage formerly demanded at distant offices was $1,20 per annum. The saving produced by the reduction of newspaper postage under the new statute, is no inconsiderable item, and many who could not afford to subscribe for the Scientific American, under the old law, can now withstand the expense. PRIZES—Our subscribers will please to consider the great inducement offered to clubs, and to keep in mind the valuable prizes offered for the four largest lists of mail subscribers. BACK NUMBERS 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 and 3—none. Of Volume 4, about 20 Nos., price 60 cts. OfVolume 5, all but four numbers, price, in sheets, $1. OfVolume 6, all; price in sheets, $2; bound, $2,75 Of Vol. 7, all; price in sheets, $2; bound, $2,75. PATENT CLAIMS—Persona desiring the claims of any invention which has been patented within fourteen years, can obtain a copy by addressing a letter to this office—stating the name of the pa tentee, and enclosing one dollar as fee for copying PATENT LAWS, AND GUIDE TO INVENTORS.—We publish, and haye for sale, the Patent Laws of the United_jftates. The pamphlet contains not only and regulation of the Patent Office. Price 121-2 cts. per copy. FOREIGN SUBSCRIBERS—Our Canada and Nova Seo-t'a patrons are solicited to compete with our oiti-zens for the valuable prizes offered on the present Volume. [It is important that all who reside out of the States should remember to send fifty cents additional to the published rates for each yearly subscriber; that amount we are obliged to pre-pay on postage.] BINDING__We would suggest to those who desire to have their volumes bound, that they had better send their numbers to this office, and have them executed in a uniform style with their previous volumes. Price of binding 75 cents. MISSING NUMBERS—Subscribers who fail to receive some of the numbers, can hava them supplied by stating what numbers are missing. INFALLIBLE BULE—It is an established rule of this office to stop sending the paper when the time for which it was pre-paid has expired, and the publishers will not deviate from that standing rule in any instance. BEOEIPTS—Whenmoney is paid at the office for subscriptions, a receipt for it will always be given, but when subscribers remit their money by mail, they may consider the arrival of the first paper'a bona-fide acknowledgment of the receipt of the funds. GIVE INTELLIGIBLE DIRECTIONS—We often receive letters with money enclosed, requesting the paper sent for the amount of the enclosure, but no name of State given, and often with the name of the post office also omitted. Persons should be careful to write their names plainly when they address publishers, and to name the post office at which they wish to receive their paper, and the State in which the post office is located. To CORRESPONDENTS—Condense your ideas into as brief space as possible, and write them out legibly, always remembering to add your name to the communication. Annonymous letters receive no attention at this office. If you have questions to ask, do it in as few words as possible, and if you have some invention to describe, come right to the business at the commencement of your letter, and not fill up the best part of your sheet in making apologies for having the presumption to address us.' We are always willing to impart information if we have the kind solicited. PATENTEES—Bemember we are always willing to execute and publish engravings of your inventions, provided they are on interesting subjects, and havft never appeared in any other publication. No engravings are inserted in our columns that have appeared in any other journal in this country, and we must be permitted to have the engraving executed to suit our own columns in size, and style. Barely the expense of the engraving is charged by us, and the wood-cuts may be claimed by the inventor, and subsequently used to advantage in other journals.