To Correspondents.—Condense your ideas into as brief space as possible, and write them out legibly, always remembering to add your name to the comajuication. 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 jour sheet in making apologies for having the presumption to address us. We are always willing to impart information if we have the kind solicited, Foreign StJBSCaiBERS.—Our Canada and Note Scotia patrons are solicited to compete with our citizens for the valuable prises offered on the nest volume. [It is important that all who reside out of the States should remember to send 25 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 hav 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 have failed to receive some of the numbers during the year, can have them supplied by stating what numbers are missing at the time of remitting for the new volume. Infallible Rtjls.—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 Receipts.—When money is paid at the offipe 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 bonafide acknowledgment of the receipt of their funds. Patent Laws, and Gcide to Inventors-—We publish, and hare for sale, the Patent Laws of the united States. The pamphlet contains not only the laws but all information touching the rules ; and regulation of the Patent Office. Price 121-2 ete. per copy. baok Numbers and Volumes—In reply to many interrogatories ae to what back numbers and t?-lumen of the Scientific American can be furnished, we make the following statement —Of Volumes i, 2 3 and 4—none. Of Vol. 5, all but six numbers, price; in sheets, $1 ; bound, $175. Of Volume 6, ftll; price in sheets, $2; bound, $2,75* Of Vol. 7 all; price in sheets, $2; bound, $2,75. Of Vol. 8, all the back numbers subsequent to No. 27, Imt none previous. Patent Claims—Persons desiring the alaims of Any inrention 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 Patentees—Remember we are always willing to execute and publish engravings of your iaventions, provided theyareon interesting subjects, and have Tor appeared in any other publication. No engraving are inserted in our columns that have appeared ia any other journal in this country, and wemust 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. Give Intelligible Directions—We often receive letters with money enclosed, requesting the paper sent or 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 papsr, and the State in which the post office is located. OThe above chapter of variety we have insert ed for the mutual benefit of our patrons and ourselves. If our subscribers will retain in mind the suggestions contained in the above paragraphs, they will be likely to be benefitted thereby; besides they will save us much valuable time and a* good deal of perplexity.