W. E. R., of N, Y.—We cannot answer your inquiry about aquarium pebbles. Write to Mr. Butler, Bar-num's Museum, this city. C. C. H., of 111.—The best CQment known to us for uniting two pieces of leather is a very strong solution of isinglass. Gutta percha dissolved in naphtha, we have been informed, is a very superior leather cement, but we have not tried it personally. Leather bands after being cemented should be allowed to dry before they are used. D. J. R, of Me.—There is no cement which can unite the two pieces of a broken knife or file, and render the tool as strong as before it was broken. Those who informed you of such a cement are mistaken. D. R R., of 111.—Marine glue is made by dissolving india rubber and shellac in naphtha. We are unacquainted with any process for bleaching it white. J. B. B., of R. L—We advise shortsighted persons, in all cases, to wear spectacles, and not try experiments for the purpose of obtaining long vision. It can't be done. J. P., of Ala.—We do not think your article, * Why dustflofttain the air," possesses sufficient general interest to war'rftnt its publication in our c5lumns. We know nothing ol the sewing machine about which you inquire. P. H. B., of Mo.—There is no monthly work issued in this country upon the subject of architecture. W. Fishbach, of Stanardsville, Va., wishes to correspond with manufacturers of screw bolts and nuts for machinery. A. N., of N. Y-—The mineral you sent us is gneiss, or ranite broken up, in its fine state, we could not say which; but it is of no uae, except, perhaps, to cover your garden walks. Q. H. G., of Mass.-The lifting power of a wooden box one cubic foot in size, and weighing four pounds, placed nnder water, is 58 pounds. The lifting power of any object placed under water is equal to the difference between the weight of that body and an equal bulk of water. A cubic f oot of water weighs 62 -5 lbs. P. M., of Pa.—You can procure a "barkometer for testing the strength of bark liquor" of Benj. Pike & Son, Broadway, New York. A. P., of HI—We do not know anything about the price, wholesale or retail, of Knapp's rosin oil. It is wholly out of our line of of business. T. R McC, of Del.—The article you send us is the oxyd of iron mixed with clay. It will make good paint for roofing purposes, but is not well adapted to the finer kinds of work. T. C. H., of Pa—A cubic foot of distilled water weighs 62?pOunds avoirdupois at a temperature of 56o Fah. E. S., of Ohio.—The reason why water rises above the surface in artesian wells is owing to the fountain-head being higher than the well surf ace. The fountain-head may be at a great distance—sometimes hundreds of miles—but it must be higher. You will find a series of illustrated articles on this subject in volume 8, Sol AJf. Tubular steam boilers are more expensive than cyunder boilers. M. R,of N. Y.—Your fountains are not patentable, although we think that the double Hero's fountain is very ingenious, and as you say, would form a very nice toy if you could get them made cheaply. You are aware that thousands are annually made in Nuremberg, and sold in all parts of Europe, but we have never seen any exactly like yours. J. J., of Me__You are about right as to the distribution of the force in your machine; but if you work the compressing air pump by an eccentric on the shaft, you will expend as much power as you gain exclusive of friction, so that you will require a small steam engine to keep your perpetual motion at work. We will pay all fees and prepare your case for nothing, when you have made this chimera work successfully. E. S. H., of N. Y.—There is no process or substance known to us by which cloth can be rendered peif ectly waterproof without being air-tight; but it may be rendered partially so, as follows:—Take four ounces of alum and one of the acetate of lead for every ten gallons of water required to cover the cloth, and boil the cloth in this solution for half &n hour, then take it out, and dry it at a heat of 212. Cloth so prepared is rendered water repellant, and if of close texture, cold water will not readily pass through it. The alum and sugar of lead should be dissolved before the cloth is put into the vesseL V. L. M.. of Pa.—No person has a right to republish a work protected by copyright under any plea, without the privilege of the person in whose name the copyright stands. If a controversial pamphlet is thus secured, and the opposing party is desirous of publishing the whole, or any material portion of it, with other matter by way of correction or reply, he will be obliged to get that privilege from the owner, or pay the usual penalty. The fact of its character being slightlyaltered by changing its title page, or asserting that the additions improved it, would make no difference. The original work is the base upon which your alleged improvements rest, and, as in patent law, you have no right to use the original without the consent of the owner. F. G. R., of Va.—Corn planters, with an apparatus for dropping and distributing guano, plaster, and other composts, are already in existence. They are commended by many, but are generally opposed on the ground that the small quantity they are able to carry is soon exhausted, and that they do not deposit the arti- cle in the proper relation to the com, and relative ) quantity to the quality of the land in which it is plant-) ed. The wonderful steam engine, " costing, indepen-L.dent of working machinery, only fifty dollars," to 3 which you refer, was evidently one of the many rotary engines which have for many years been got up with a view of superseding the reciprocating engine. Money received at the Scientific American Office on account of Patent Office business, for the weekending Saturday, May 1, 1858 :- E. J., of Conn., $30; M. G., of Pa., $25 ; W. H., of Ohio, $30; H. D. W., of Mich., $30 ; L. L. C, of N. Y., $55 : J. A., of Pa., $33 ; J. R T., of Pa., $55 ; J. & D., of N. Y., $30 ; C. D., of N. Y., $30; O. S., of N. Y., $30 ; G. W., of Conn., $30; J. L., of Mass., $20; W. C, of Mass., $25; A. S. S., of Mass., $25; F. & Co., of Conn., $25; S. H. Jr., of N. H., $25 ; J. C, of N. Y.. $30; E. T. B., of Ga., $65; E. M., of N. Y., $30; W. S. H., of N. J., $10 ; T. W. Jr., of Conn., $30; S. T., of Mich., $25; B. & W., of Pa., $30; E S.. of La., $30; T. & S., of Pa., $10; S. B., of Ohio, $55; H. & S., of N. Y., $40; J. M., of Iowa, $10; A. C, of N. Y., $25; G. E. C, of Minn., $33 ; J. W. W., of Ind., $30; C. McL, of N. J.. $20; G. M. L. McM., of Ohio, $25; A J. D., of Cal., $5; W. B. C, of Pa., $30; D. & M., of HI., $15; L C., of N. Y., $25; J. R, of Ohio, $30; W. H. R., of Fla., $100; R. & S., of Ohio, $25; G. W. S., of 111.,$25; D. Y. C, of Pa., $30; B. R, of Mass., $30; W. H., of N. Y., $25; J. H. R, of N. Y., $60; W. G. B., of N. Y., $25; H. G. D., of Ky., $35 ; A. McK, of N. Y., $: A. P. & Co., of Cal., $60. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday, May 1,1858:- W. G. R, of N. Y. ; J. Y. L., of N. Y.; J. H. R, of N. Y., (2 cases); C. McL, of N. J.; H. G. D., of Ky. ; S. H. Jr., of N. H.; A. S. S., of Mass.; F. & Co.. of Conn.; J. C.,of N. Y.; M. G.,of Pa.; W. C, of Mass.; L C, of N. Y. ; G. M. L. McM., of Ohio ; B. & W., of Pa.; S. T., of Mich.; E. S., of La.; A. C, of N. Y.; N. H., of Pa.; A. McK., of N. Y.
This article was originally published with the title "Correspondents" in Scientific American 13, 35, 279 (May 1858)