CORRESPONDENTS who expect to receive answers to their letters must, m all cases, siffn their names. We have a right to know those who seek information from us; beside, as sometimes happens, we may prefer to address correspondents by mail. PEGIAL NO TE.— This column is desianed for the general interest and instruction of our readers,not for gratuitous replies to questions of a purely business or pmsonal nature. We will publish such inquiries, however-when paid for as advertisemets at $1*00 a line, under the head of Business and Personal." All reference to back numbers should be by volume and page. S. T. D., of Me.—It will take less power to work a force pump having a feed pipe larger than a discharge pipe, where the capacity of the pump is sufficient to supply the full capacity of the discharge. The rea- ( sons are, that atmospheric pressure can only force water through a pipe Ot given ste ft a yen yelQcity, no rositter IQw fagt jqmv pump is worl?eC ) If the pump has not capacity to force out water through the discharge ' pipe beyond the limit of supply through a feed pipe of given size, the feed pipe need not be enlarged ; but force pumps, as a rule, work under more . 1;han atmospheric pressure, and consequently will discharge watei through a pipe faster than the same sized pipe would supply it under at-L mospheric pressure. The friction is also less in a large feed pipe. Undei the circumstances you describe, where the feed water has to be raised 2( 5 feet and forced through an orifice of IK inches, we think the feedpipe ought to be at least 2 inches. The making the feed pipe of a pump too small is a common mistake. The feed water is raised only by atmospheric pressure,15 pounds, while a much larger pressure is applied to the plunger of the pump. Under such circumstances the water will not be supplied to the pump with sufficient rapidity to meet the demand. If the water in your pump is forced out with great velocity, you may need to employ a still larger feed pipe to obtain satisfactory results. . ; J. P. D., of La.—The breaking of inferior qualities of glass in ' in the manner described is not confined to lamp chimneys, although from the many changes in temperature to which they are subjected, it is more I frequent with them. The difficulty is in the quality of the glass, both its composition and the annealing, are frequently at fault. The breaking of k these chimnejtglassesis a great annoyance, and it is to be hoped that i some inventor will give us yet a lamp that will not require a chimney. The only way to prevent in any measure this breakage, is to anneal the chimneys yourself before using them by heating them very hot and allow- ing them to cool slowly, but few have appliances to do this efficiently and ; without risk to the chimneys. W. C. T., of Ga.—The crystals you send have no value. They are composed of quartz or silica, which Is one of the most abundant and hardest of minerals, and is a constituent of many kinds of rocks. Silica does not melt under the blow pipe or dissolve in water. The dark colored mineral appears to be a form of limestone containing iron and other min'erals, and is apparently of no value. It is, of course, impossible to state the exact constituents of a mineral specimen withoutmaking a careful chemical analysis. A. R., off N. J.—The question whether a given amount of heat will develop more steam in a given time from boiling water than from water before it boils, is yet undecided. Dr. Ure thinks that boiling favors the escape of steam. We have never seen, however, any experiments, or recorded results of experiments, which are conclusive on this point. Our own opinion is that should any such experiments be tried no difference would be found. A. R., of Pa.—The notion that a boiler sustains more pressure at the top than the bottom is an absurd mistake. The reverse is true, as in addition to the pressure of the steam above the water, there is the hydraulic pressure of the water on the bottom. ASjhoweifcer, the hight of the waterin a boiler is not generally great, there is not much difference. It is not a fact that all boilers burst at the top. W. F. D., of N. H.—There would be no very material differ-ejice in the amount of friction in water flowing through two pipes of the same size and form, one made of cast-iron and the other of cement. A good cement pipe is as cheap as anything we know of equally efflcient. Your other inquiry requires a mathematical calculation, for which you should apply to an hydraulic engineer inclosing five dollars. J. 0. L., of 111.—Vv e do not know enough of the device you describe to say whether it contains any points of novelty. The idea of propelling a wind wheel by upward currents through a chimney stack is notby any means new, but the method of doing it in this case may be. There is no doubt that a considerable power might be obtained in this way in a tall chimney, but it would be at the expense of the draft. T. P., of La.—The species of silk worm you ask about, the i natural food of which is the foliage of the oak, imported to the southern part of Austria and France from Japan, have not, to our knowledge, ever beenbroughtto this country. Should any of our correspondents happen to know of a trial of this species in the United States, we should be happy to hear from him. F. K. IL, of Ohio.—To make the finest piano finish on walnut chestnut, or other open and coarse-grained woods, it is usual to use a coarse kind of varnish called scraping varnish. A heavy coat of this is laid on the raw wood, and then the surface is scraped with steel scrapers. ! It is then varnished with a better quality of varnish, rubbed down perfectly smooth with pumice stone,and finally flowed with the best kind of ' varnish. B. P. A., of S. C.—The advantages of the hydrostatic press over all others known for cerjjin kinds of work, ate enormous power in small compass, with less friction and perfect control, both as to the extent of motion in the platen and the amount of power applied. Your device is not new in principle. A patent would not be granted for it. C. W. C, of Pa.—The circumstances which compel the removal of your chimney stack so faraway from the furnaces are unfortunate, as they will compel you to run your chimney up higher to get the proper draft. We should think thirty feet additional hight would not morethan fully compensate for the difference in position. W. H. C, of N. Y.—Simply exhausting a receiver by means of an air pump, can never give any pressure upon its exterior greater than it sustains at all times, both before ana after exhaustion. It simply re moves atmospheric pressure from the interior. S. T. B., of Ga.—One of the minerals you sena appears to be a soft conglomerate of quartz and feldspar, of no value. We find gold in the other specimen, and it appears to be gold-bearing quartz whicli may be valuable. You should have it analyzed. J. W. C, of Mich.—You can not profitably extract the sugar from cream sirups which have soured. —The cost of binding the Scibis"-TiFio Amekioak in this city is $1-50 per volume. " Pioneer Maggie."—A correspondent wishes to know the name of the builder of the above-named yacht. We do not know, b-ut Henry Steers, of this city, builds first-class yachts. W. S. P., of Mass.—The origin oi yeast is obscure, like the origin of every other existence. Assuming the existence of a first cause, we maintain that it is not a subject for physical inquiry. Somewhere the mind must stop at a cause uncaused, a subject for faith not demonstration. E. Q. F,, of Me.—The crank is to be regarded as a lever only, the fulcrum being the center of the axle, and the resistance being applied at the circumference of the axle, the point of application of the power being the center of the crania-wrist. Inventions Patented in England ly Americans, [Compiled from the "Journal of the Commissioners of Patents."] PROTISIONAL PROTECTION FOR SIX MONTHS. 2,350.—NiTMBEiMir& Reohstek.—G. Sickels and J. H. Thorndike, Boston, Mass. August 6,1869. ' HoLDEBs fob the Chtmiets of Gas Bueneks.—Elliott P. Glcasou, New York city. August 6, 1869. 2,378.—Meaits fob Cabbtt& ob Stobing Eg&s.—P. P. Josef, Buffalo, N. Y. August 9,1869. 2,392.—Adding Appabatus.—C. Henry Webb, New York city. August 9, 1869. 2,892.—Tbeatment of Conglomebates f Cast Ibon, etc.—T. S. Blair, Pittsburgh, Pa. August 10, 1869. 2,416.—MACHiifEBT fob CHABGIN-& Gas Eetoets.—N. O. J. Tinsdalc, New Orleans, La, August 12,1869. 2,425.—ExTBACTiNG COPPEB FBOM its Obes.-T. S, Hunt, Montrefil, and DOUSlag, Jr., Quebec, Canada., August 15,1869, ]
This article was originally published with the title "Answers to Correspondents"