Heat from Percussion and Heat from Friction. MESSRS. EDITORS :—On page 149, current volume, under the head of “Hammering Iron until it i& Red Hot,” I find the following, which I quote : “It has been asked whether iron ' could be hammered cold until it became red hot.” And it is stated that, as an experiment to prove the affirmative, “when a piece of very tough iron was hammered with a moderately heavy hammer it became hot, but would not scorch a piece of paper. It was then hammered by two men, one of whom used a sledge hammer, but with no better result. Presently another workman took a horseshoe nail, and after hammering for less than two minutes with a light hdnmer part of the nail was brought to a bright'red heat. The blows were light but frequent, and the nail was partly turned at each blow." Now, is this not in strict accordance with the vibratory theory of heat ? No doubt a great part of the, muscular force imparted to the hammer was, in both cases, changed into sonorous vibrations in the material sustaining the shock ; this, of course, would produce the sensation of souni. instead of heat 1 The blows of the heavy hammer did not, directly, produce heat, but as the iron was not sufficiently elastic to recover from so great a compression, it was condensed, which caused a certain part of its latent heat to become sensible, but beyond this nothing wilts obtained. The light hammer, if at all, condensed the iron very little, and, the blows being “ light but frequent,” its force was expended in producing the very rapid molecular vibrations neaessary in bringing it to the red heat which it acquired. The human arm is incapable of striking very rapid blows, but if to the periphery of a wheel a series of small hammers be attached so that by the revolution of the wheel they will rapidly and in succession strike on a piece of iron it would probably produce a red helft much sooner than is possible by the hand alone. By greatly reducing the siza of the hammers and increasing their number we would nearly approach what would seem to be the best mode of producing the desired result, Now let us look at the file, the saw, and the grindstone, and see if they do not furnish direct proof in support of theory. What else than peftlussion would a piece of iron receive if pressed against the teeth of a revolving circular saw ? Except the saw be put in too rapid motion the jumping Tjf the iron from one tooth to the next would, in effect, be the same as so many distinct blows. The same holds in relation to the grindsTone. As it revolves hold one end of a nail against it, and it will soon, by leaping from one granule of the stone to another, acquire such an inconceivably rapid mSlecular vibratory motion as to become red hot. That a piece of iron under these conditions will Boon become intensely hot is well known. The coarser the grit of the stone the more apparently is its action analogous to percussion. ; These remarks lead us to see the close connection between friction and percussion—the one being insensibly graduated into the other ; the difference is only in degree. Who can draw a line of separation ? Spectrum. Havana, N. Y. TIle Gerner Boiler. ' Messrs. Editors :—Permit us to correct an error in your statement, in your issue of October 9, respecting the amount of heating surface in the small Gerner boiler you tested at Paterson, N. J. The boiler is 10 feet long, 2 feet front, and 3 feet rear diameter, giving a total heating surface of 83No square feet, instead of 144, as stated. The results obtained by you being over 15-horse power shows 5t square feet in these boilers to be sufficient to produce a horse power, and illustrates the efficiency of the heating surface.” Kasson&Co. New York city. On the Flow of Elastic Fluids. Messrs. Editors :—On pages 50 and 118, of the current volume of the Scientific American, are articles '.' On th.., Flow of Elastic Fluids through Orifices or Pipes.” The theory of this subject which appears to be accepted by the writers of these articles, is the old theory, and the only one, so far as I know, that has as yet found its way into treatises on physics. It is, however, a theory which is widely at variance both with sound theoretical philosophy and with the results of experiment. It is, in fact, nothing more than the theory of inelastic and inexpansible fluids applied to those which are elastic and expansible ; it being assumed that there is no difference between the two in respect to the law of their flow except what is due to the smaller ratio of weight to pressure in the elastic fluids. The effect of the expansibility of elastic fluids is such as to take them entirely out of the law which govcwns the flow of those that are inelastic. It causes.the flow into a vacuum in a given time to be only half as great as the old theory calls for; and this, not because the velocity of the flow is less than that theory assigns, but because the density of the flow is only half as great as the theory assumes it to be. Another curious and important fact which results from the expansibility of a fluid, is that when it flows trom one vessel into another containing fluid of less density, the fluid in the receiving vessel has no effect whatever to obstruct or retard the flow, unless its density exceeds half the density of that in the other vessel. In other words, steam _ at 20 pounds pressure in the cylinder, will discharge itself into the condenser already containing steam, of not exceeding 10 pounds, just as © 1869 SCIENTIFIC AMERICAN, INC. October 16, 1869.] 247 rapidly as into a perfect vacuum. The bearing of these facts on the question of the proper size for ports and pipes in steam engines will be readily seen. It appears from the first clause of the article on page 50, that some of the readers of the Scientific American are seeking information on this subject. I would refer such to the American Journal of Science, 2d series, vol. 5, page 78, where they will find the true law of the flow of elastic fluids Bet forth and mathematically demonstrated, and to vol. 12, page 186 of the same journal, where they will find the same law completely confirmed by experiment. New Haven, Conn. Eli W. Blake. Business Correspondence. Messrs. Mtjnn&Co.:—I herewith acknowledge the receipt of the official notice allowing a patent for my Can Opener, and I deem it my duty to thank you for your prompt and able management of my case. This is the third patent which you have obtained for me this year. I have received several circulars from various patent attorneys residing in Washington, who offer their services free of charge until a patent is obtained. But I assure you, gentlemen, that I would sooner pay you your charges in advance, and run the risk of losing the amount along with the first Government fees, than to trust such agents with any business of mine, Therefore I care not whether they are capable or honest so long as I am satisfied with your manner of doing business. I will cordially recommend your Agency to such of my friends as may need the assistance of patent attorneys. I am, sirs, very respectfully yours, Wm. M. Bleakley. Verplanck, N. T., Sept. 29, 1869. Messrs. M.unn&Co.:—I have received the two patents, one on a Bolt Heading the other on a Hook-Bending Machine, which you have obtained for me.' Allow me to express my appreciation of the able manner in which my specifications and claims have been prepared, and to thank you for having so speedily obtained favorable decisions from the Patent Office. • Any influence which I can have in this part of the country, I assure you will be in your favor. Truly yours, - D. G, MORRIS. Catasauqua, Pa. , Sept. 16, 1869. Messrs. Munn&Co. :—1 received the patent on the 17th and the copies on the 20th. I am so well satisfied with the manner in which you prosecuted the application to a successful termination that I shall give 3011 such business to you in the future, and will influence any person—needing the services of a trustworthy and intelligent attorney—among my acquaintances, to give their business into your hands. I am truly yours, Levi S. Ives. Pittsburgh, Pa., Sept. 21, 1869. Messrs. Munn&Co. :—We have received our patent, and are highly pleased with the way in which the business has done. The ability which carried it through, and the care bestowed on its preparation, are above praise, and we will gladly intrust to your hands any further business we may have to do. Very truly yours, J. H. Wildasin&J. A. Peck. St. Charles, Iowa, Sept. 24. 1869. [We arc constantly receiving warm commendatory letters like the above, from our many clients. The Patent Soliciting Department of this Office is going on with marked success, and inventors who contemplate taking out patents for their improvements can always avail themselves of our advice and assistance on the most favorable terms,—JDDS. New Cornish Engine. We learn from the Press (Philadelphia) that the Cornish engine just started to work at the Schuylkill Works differs from the ordinary Cornish engines in having the heavy lever beams placed down upon each side of the cylinder, with their bearings ''resting directly upon the bed-plate and stone foundation, instead of over the cylinder, in the usual manner. By this plan much greater stability is secured, and expensive alterations and additions, which would have been necessary with the ordinary form of engine, were avoided, The size of the steam cylinder is 72 inches diameter and ten feet stroke,. and the pump plunger is 36 inches diameter and ten feet stroke. The beams weigh about 28,000 pounds each, and the load in the plunger is about 60,000 pounds, This machine is capable of raising 7,500,000 gallons of water per twenty-four hours. The action of the engine is peculiar. The steam is admitted upon the top of the cylinder, and after the piston has passed through.about one-third of its stroke, the steam is cut off, the rest of the stroke being made by the expansion of the steam in the cylinder. The plunger has now been raised to the top of its stroke; a valve is then opened allowing the steam on the top of the piston to pass to the underside of it, thus putting an equal pressure on both sides of it, and allowing the plunger and its weight to fall by its own gravity and thus force the water to the reservoir. It will be seen that this plunger must, therefore, be heavy enough to lift the load of water in the main, and also to overcome the friction of the water in the pump and pipes. The engine was designed by tho Chief Engineer of the Water Department, Frederick Graff. fn order to be able to make the contractors for the building of the engine (Messrs. Merrick&Sons) entirely liable, they were intrusted with the design for the details of parts, and are by their contract held responsible for the strength and proportions of these details, The engine is a splendid specimen of massive machinery, and reflects great credit upon Mr. Graff and Messrs. Merrick&Sons. The water is forced into the stand-pipe at the works, 1 and thence through a main 36 inches in diameter and 312 feet long to the reservoir. The engine is rt present worked by the old boilers. The appropriation for the new set of boilers intended for her was delayed more than eight months by the refusal of the Democratic members of Select Council to vote for the loan asked for their erection. They are now in place at the works, and will be put into use in a few weeks. (For the Scientific American.)