From the success of the Atlantic Cable, corres pondents will at once see the propriety of our omitting their articles on the enbject oflts failure. H. J. It, of Va.—Very fine impressions of ferns may be obtained by thorougbly saturating tbem in common porter, and laying them flat between white sheets of paper without much pressure, and letting tbem dry out. J. G., of DeL—Revolving sails have often been suggested a3 a means for propeliing and guiding balloons. We have no confidence* in tbe success of any sucb scheme. M. G., of Ohio.—Tbe exclusive claim which your employer sets up to an invention made by you, because you happened then to workfor him, reminds us of a New Zealand chief, who maintained that he had a good title to his land because be had eaten the former owner. The claim of your employer will not avail, unless by special contract you made the invention for him. You had better proceed at once to apply for the patent. Inventors many times lose the full benefit of their improvements by unneceosary delays. C. L. McGrew, I.exington. Mo., whes to purchase an engine pump capable of drawing water about thirty feet through a two and a-half inch pipe, and thence forcing it to the top of a three or four-story building, to be used as a fire-extinguisher. C. C., of Conn.—The amount of force exerted by one pound of gunpowder is 221,240 pouuds raised onc foot high. W. H. S., of PhiIa.—Orfila's celebrated hair dye Is said to be simply carbonate of lime, made by boiling, for an hour and a quarter, fourarts of sulphate of lime with five prts of slaked lime, In thirty parts of water. i Filter the liquor and collect the powder, which, if applied in a warm solution, will dye the llalr a fine black in one hour. S. 0., of Conn.—The best method that we can recommend you to adopt for protecting yom shingles is to kyanize them, or give them a coat of red lead and boiled oil before using. J. S. It, of IlL—The bait used by English and other rat-catchers to tempt the wily animals Into their wire prisons, Is the oil of rhodium, for which rats bave as great a partiality as cats have for their peculiar h nip.tt B. S.,of Md.—Tbe breaking strain given inanItem on wire rope, a few weeks ago. was the amount to each square inch. The British government require that all wrought iron furnished to themshallsustain the weigbt often tuns to the sectional square inch. J. Q., of-----.—YOUt suggestions concerning the At. lantic Cable are old, and have been decided to be useless. M. A. S., of lll.—The best method of constructing an ice house Is to buiM its walls entirely underground, with a foot spaee outside -for rice, chaff, charcoal, sawdust, or other good non-conducting material. The covering, and other part! above ground, should also be made double, and filled in with the .ame non-conducting substauce. W. K,, of Ill.—The employment of ambrotypes, or pictures taken on glaas. for magic lantern purposes, in the manner you Indicate, has been done before, and Ismis not therefore patentable. W. H. R., of Va.—Railroad station indicators made as you propose, to wit, the names of the stations painted on au endless belt moved by a crank, are qulte old. Your device is not patentable. A. M., of Iowa.—By covering common bricks with common salt, and heating them until the whole surface is glazed, they will be protected from the action of the weather, and have a hard, durable, and vitreous coating. J. M. A., of R. I.—Your engine is wbat is variously known as U Hornblower's engine," and "Wolff's engine," and was invented by Hornblower nearly eighty years ago. Such engines, with cylinders side by side, are now, or were, many years ago, in use on some English steamers. But this method of nsing steam is not so good as using it with a high degree of expansion In a single cylinder. Money received at the Scientific American Office on account of Patent Office business, for tbe week endins Saturday, August 7,1858 :— J. H. C., of N. Y., $100: W. C, of N. J., $30: W. A. M., of Minn., $27: W. D., of Texas, $25: W. D., of N. J., $25: J. A. McC., of N. Y., $25: J. P. a, of N. Y., $30: R. H. E., of Ill., $35: W. M. S., of N. Y., $25; A, W. IL, of onn., $25: J. W. M., of Pa., $35; J. L., of Mass $35; G. C., of Ky., $30; J. C. F., of Texas, $35; W. W. H., of Texas, $30; H. H., of Ind. $30; J. M. B. of-----, $30; J. A., Jr., of Mass., $30 ; O. H. S. a, ofInd.,$27: M. & W.,ofIll., $25; T.E. McN.,ofPa., $55; W. H. T., of Mass., $30; a 0., of Ohio, $27: E. M. B., of Wis., $55; A, P., of Tenn:, $25; E. D., of Md., $250; W. G. &, of Ill. $30; A. S. M., of S. C., $55; J. P. E., of Pa.. $35; A. F. T., of Mass., $55; G. & D., of Texas, $30; A. S., of PIL, $30; A. S. S., of Obio, $25; W. G. a, of III., $30; I. M. M., of Ind., $30; a P. a, of Pa., $35: B. & H., of Mass., $32; J. W. N., oC Conn., $32 ; T. W. a, of N. Y.,$l00: T. H., of Ohio,$3l; J.A-,ofS. C.,$5; A. H., of N. Y., $30: K. F. of Wis., $25; M. A. W., of Ohio, $15 ; J. K., of N. Y., $25: J. R., of Mass., $30. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office dur:", the week ending Saturday,August 7,1%8:— O. H. S. a, of Ind. : C. P. G., of IU.: J. C. F., of Oblo; A. P., of Tenn. ; J. K. of N. Y. ; K F., of Wis.; J. C. F., of Texas; J. H.,ofN.Y. ; a P. a,of Pa.; T. H., of Oblo; A. W. H., of Conn. ; J. M-, of Iowa ; J. L., of Mass.: W. D., or N. J. ; a O., of Ohio j J. A.,ofS. C.: M. A. W. of Ohio; W. A. M-, of (Minn.
This article was originally published with the title "Correspondents" in Scientific American 13, 49, 391 (August 1858)