L. B. V., of N. Y.—See Mr. Lester's advertisement on another page, for a good planing machine. We are not acquainted with a whitewash that rill last for three yeivrs ; but ;i cheap paint, composed of dry clay and sand in powder, some whiting, red lead, and linseed oil, will perhaps answer your purpose. J. N. C., of Ohio.—You state that you have bought a patent recipe for making a paint, and have desciibed it as a composition of shellac varnish and common paint, but say that while you can cut the varnish, you cannot mix it with the paint, and wish us to tell you how to mix it. Why don't you inquire of the person from whom you bought the recipe ? He is bound to tell you, for " value received." We do not know why you have found difficulty in mixing paint with lac varnish. We can do it without any trouble ; never heard of any difficulty experienced before your case. J. F. P., of N. Y—You state that you cannot fill your iron molds in making brass castings, and that you are unable to find out the cause. We do not know wherein the error in casting exists, but the result undoubtedly points to a defect in venting the mold. Some air, Ave think, must be retained inside, which prevents the brass filling the entire interior. J. T., of Maine.—We presume you do" not moan whalebone buttons, but those made of a composition of india rubber resembling whalebone, which arc now in common use. We are not acquainted with the manufacture of whalebone buttons. D. B. T., of Ohio.—Your suggestion to make an excavation large and deep enough to hold sufficient water to float the LeySalhan, has been proposed to us several times. It has not escaped the attention of English engineers. J. R., of La.—We arc in receipt of your Letters Patent and $20. The engravings will appear in our paper in about two weeks. J. S., of Ohio.—You have made the water of your cistern clear by throwing some alum water into it, and you now find that the water is hard, and curdles soap. You can render it soft again by the use of some soda ash in solution. If you employ the water for drinking, be very careful and use only a very small quantity of the soda ; for washing purposes you need not be so particular. % M. B. B., of N. Y.—We have examined your sketch of the double-acting pump, but do not find any patentable feature in it. It is not new to work the piston of one cylinder by a rod passing through the hollow red of the other piston. The ill-fated steamer Pacific was not 300 feet long ; the Persia is 360, the Adriatic 354, and the Leviathan 700 feet long. C. B. IL, of N. Y—The cost of a nautical almanac is fifty cent,s ; you can obtain it from R. L. Shaw, No. 222 Water street, this city. H, C. S., of N. Y—We do not know what kind of oil the " lunar" is. We think it is a coal oil with a flash name. The agents who sell it can tell, if they will ; ask them about it. L. A., of Mass.—There is no power gained by the use of a balance wheel. It is a regulator and accumulator of power. You will obtain no advantage from one on the shaft of a circular saw driven by a belt ; if it were a reciprocating saw, it would be advantageous. W. Q.. of Pa.—To obtain the information you want in reference to the velocipede patented by Kellner, you should order a copy of his patent from the Commissioner of Patents. F. B. W*., of 111.—The case you suppose is one that never could occur, as a syphon will only work when the delivery tube is longer than the receiving tube. In the first example, the water would rise up the tube just so long as the atmospheric pressure was excluded by mechanical means, as an air-pump ; but the moment you remove the air-pump, the air presses just the same on the mouth of the tube as on the water in the well, so that it would again fall to its original level. J. T. IL, of Tenn.—We are not aware of having received a letter from you before. You can correspond with us again. We mean to neglect no ono who complies with our rules in such matters. S. Marshall, of Wilmington, Del., wishes to correspond with different manufacturera of carriage knobs in America and England. A. B., of Ohio.—Gun barrels are browned by rubbing their surface with a weak solution of nitric acid and sulphate of copper, and setting them aside for a few days until they are coated with rust. This is then brushed off; the barrel washed in warm water, dried, and rubbed up with a little wax dissolved in turpentine. Two and three coati -gs of the acid ar2 sometimes required to bite a suffi ci?: c depth into the metal. E. E. W., of N. H__I Smee's Electro Metallurgy," you will find a full de u ription of the processes for multiplying daguerreotype pictures, also etching pictures by the galvanic battery. E. C. M., of N. Y.-We decline publishing your communication, as it does not, in our opinion, throw any light on the phenomena of the remains of tropical plants and animals now found in the arctic regions. You have advanced no facts to prove that the moon once formed part of the earth, and was shot from the bed of the Pacific or Atlantic oceans as you assert, b> a great steam explosion caused by the water getting int(. the red-hot interior of the globe. J. T., of Ohio—There is no power in a lever ; it only becomes a mechanical power when force is communicated to it. Those neighbors of yours WIK intend to derive as much power from a long lever as will irivf l our-horae threshing machine are not acquainto twit the " laws of mechanics." You are safe in agrc t ing o pay all the expense, if it operates. A. F., of Mass.—You ask the question, "H the right to buy up second-hand patented machines and | repair them, even to making all the essential new, so long as the original table or frame is used in the same Territory in which they were originally sold to be used ?" To replace the essential worn out parts of a patented machine on an old frame is nothing less than making a new machine. Unless you own the patent right, you cannot. As a mechanic, you can repair any broken part of a patented machine for others. M. B. F., of N. Y.—Make your gang pulleys as follows, and you will have them arranged so as to run one-twtlfth slower each set off. Driver shaft first pulley, 8-inch ; driven pulley, 4-inch ; second driver, 7 13-17-in., driven 4 4-17 ; third driver, 7M-in. driven A% ; fourth, 71-5 in. driven 4-4-5. This proportion of pulleys will enable you to decrease the speed of the driven shaft one-twelfth with every change of the same belt, so as to run your cards with the speed desired. Money received at the Scientific American Office on account of Patent Office business, for the week ending Saturday, January 30, 1858 :— F. II. S., of Conn., $25 ; T. G., of Pa., $0. S. L. W. of Pa., $150; N. S., of La., $30; J. P. M., of R. L, $30; A. F. F., of Vt., $30; A. B. IL, of N. Y.. $30 ; C. W., of Pa., $25; M. G., of Pa., $25 ; C. Van DeW., of Mass., $27; J. B. F., ofWis., $30; J. II., of N.Y.. $25 ; F. & Co., of N. Y., $250 : C. & M., of Iowa, $20 II. A. W., of N. Y., $25 ; J. T., of N. J., $10; T. V., of Cal., $27 ; C. 13. G., of Pa., $30 ; W. I. M., of Conn., $30 ; S. G., of Mich., $50 ; T. A. D., of N. Y., $10 ; W. & C, of Conn., $32 ; T. & B., of N. Y., $45 ; S. C, of N. Y., $30 ; F. P. A. Jr. of Conn., $ 25 ; A. B., of Ohio $2S ; E. K, of Pa., $30 ; J. P. W. D., of Ind., $30 ; J W. F., of Mo., $35 ; L. D. of N. Y., $20 ; S. H. G , of Conn., $30 ; A. E. L., of Pa., $15 ; C. B. C, of N. Y. $20 ; II. & Co., of N. Y ,$57 ; F. C. G., of N. J., $20. Specifications and dra wings belonging to parties with the following initials ha ve been forwarded to the Patent Office during the week ending Saturday, January 30,1858 :— C. & M., of Iowa C. B. C, of N. Y. ; J. D., of N. Y. ; W. G. S., of Mass. ; L. R., of Mass. ; II. A. W., of N. Y. ; T. G., of Pa. ; M. G., of Pa. ; J. IL, of N. Y. ; C. Van DeW., of Maas. ; F. IL S., of Conn. ; N. W., of Conn. ; A. B., of Ohio ; W. McK., of Cal. ; T. V., of Cal. ; F. C. G., of N. J. ; W. W. D., of Cal. ; L. D., of N. Y. ; I. C, of Vt. ; A. L., of Conn. ; T. R , of Pa. T. D. I., of Mich, ; W. O. IL, of Pa. ; A B , of N. Y. S. G. Jr., of N. Y. ; J. A. B., of Mass. Important to Inventors THE RAPID GROWTH OF OUR PATENT Agency business during the past three years has required a great addition to our ordinary facilities for its performance, and Ave are now able to announce the completion of a system which cannot fail to arrest the attention of all who have business of this kind to transact. OUR PRINCIPAL OFFICE will ba, as usual, at No. 128 Fulton street, New York. There is no other city in the Union so easy of access from every quarter as this, consequently there are greater advantages in regard to the transmission of models, funds, &c, through the various channels that center in New York. Two of the partners of our firm reside here, and during the hours of business arc always at hand to counsel and advise with inventors. They are assisted by a corps of skillful Examiners, who have had many years of active experience in the preparation of cases for the Patent Office. Torenderour Patent Agency Department complete in every respect, we have established a BRANCH OFFICE IN THE CITY OF WASHINGTON, on the corner of F. and Seventh streets, opposite the United States Patent Office. This office is under the general ctf of one of the firm, assisted by experienced Examiners. The Branch Office is in daily communication with the Principal Office in New York, and personal attention will be given at the Patent Ofico to all such cases as may require it. Inventors and others who may visit Washington, having business at the Patent Office, are cordially invited to call at our office. A SPECIAL NOTICE. We especially require that all letters, models and remittances should be made to our address at New York. EXAMINATION OF INVENTIONS. We have been accustomed from the commencement of our business—twelve years since—to examine sketches and descriptions, and give advice in regard to the novelty of new inventions, without charge. We also furnish a printed circular of information to all who nrny wish it, giving instructions as to the proper method which should be adopted in making applications. This practice we shall still continue, and it is our purpose at all times to give such advice free and candidly to all who apply to us. In no case toill we advise an inventor to make application unless toe have confidence in his success before the Patent Office. Our extensiveexperience in mechanical and chemical improvements enables us to decide adversely to nearly one half of the cases presented to us for our opinion, before any expense has occurred in the preparation of the case for a patent. When doubt exists in regard to the novelty of an invention, we advise in such cases a PRELIMINARY EXAMINATION to be made at the Patent Office. We are prepared to conduct such examinations at the Patent Office through our " Branch Agency," upon being furnished with a sketch and description of the improvement. Our fee for this service will be $5. After sufficient experience under this system, we confidently recommend it as a safe precautionary step in all cases before application is made for a patent—not that there will h\u>t rtke=?m mulc-r thlr Hv-eisi* Icis impossible to avoid siren requit-* in ltnny casr?, owinr to the exceedingly wide range taken by \\\vt Examiners in the examination of cases; but, nevertheless, many applicants will be saved the expense of an application by adopting this course. Applicants who expect answers by mail must enclose sta mps to pay return postage. THE COSTS ATTENDING AN APPLICATION for a p.itent through our agency are very moderate, and great care is exercised in their preparation. No cases are lost for want of care on our part in drawing up the papers, and if the claims are rejected, we enter upon a speedy examination of the reasons assigned by the Commissioner of Patents for the refusal, and make a report to our clients as to the prospects of success by further prosecution. A circular containing fuller information respecting the method of applying for patenta can be had gratis at either of our offices. REJECTED APPLICATIONS. We are prepared to undertake the investigation and prosecution of rejected cases, on reasonable terms. The close proximity of our Washington Agency to the Patent Office afiords us rare opportunities for the examination and comparison of reference?, models, dritwinga, documents, &c. Our success in the prosecution of rejected cases has been vrry great. The principal portion of our ; charge is generally left dependent upon the final result. ! All personshavingrejected cases which they desire to have prosecuted are invited to correspond with us on the subject, giving abrief history of their case, enclosing the official letters,&c. FOREIGN PATENTS. We are very extensively engaged in the preparation and securing of patents in the various European countries. For the transaction of this business we have ! offices at Nos. 06 Chancery Lane, London ; 29Boulevard I Saint Martin, Paris ; and 3 Rue Therrsienne, Brussels. ! We think we may safely say that three-fourths of all I the European patents secured to American citizens are ' procured through our Agency. ; Inventors tvill do well to bear in mind that the English law does not limit the issue of patents to inventors. Any one can take out a patent there. Circulars of information sent free on application. tr Remember the SCIENTIFIC AMERICAN PATENT AGENCY, No. 128 Fulton street, New York. MUNN & COMPANY, Proprietors. The annexed letter from the late Commissioner of Patents we commend to the perusal of all persons interested in obtaining patents :— MESSRS. MUNN & Co.—I take pleasure in stating that while I held the office of Commissioner of Patents, MOKE THAN ONE-FOURTH OF AT.L THE BUSINESS OP THE OFFICE came through your hands. I have no doubt that the public confidence thus indicated has been fully deserved, as I have always observed, in all your intercourse with the Office, a marked degree of promptness, skill, and fidelity to the interests of your employers. Yours, very truly, CHAS. MASON.
This article was originally published with the title "Correspondents"