This method of operating hammers ior driving piles and for other purposes, is now attracting great attention in the engineering world. The machine is constructed of heavy wood framing, as in the ordinary pile driving macMne, and is provided with a cylinder head of cast iron, K, resting on the top of the pile, C, and guided by the iron rails, N; the cylinder is bored out on its upper end for the reception of a plunger, S, of the hammer, H, and iscast concave on its lower end for the reception of the pile,C. The hammer, H, is guided by the rails, N, (the same as the cylinder)and is bored on its upper end for the reception of apiston.I. It is cast, with a V-groove for the reception of a friction rod, M, Pig. 2, to be used as hereafter describ ed. The piston and rod, I, are connected with a cross beam, firmly fixed at the top of the frame, where a rope pulley, F, is also placed for the convenience of hoisting the piles in position. The friction rod, M, is connected with the starting lever, O, and also with short cast-iron arms pivoted to brackets, L, Pigs. 1 and 2,for the purpose of pressing tightly against the V-groove in the hammer, as shown in Fig. 2, whenever the hammer moves in a downward direction. A ring is made of steel and screwed on the end of plunger, S; this ring.though of solid steel, expands under this pressure, the same as hydraulic packing, and makes a tight and durable packing. The machine is operated and controlled by a man and boy; the latter is stationed at the rope ladder, G, and throws a cartridge of powder into the cylinder, K; when the hammer is allowed to drop by the man's pressing upon the lever, Q, which elevates and releases the friction rod from the hammer and causes it to drop, forcing its plunger into the cylinder.compressing and heating the air contained therein sufficient to ignite the powder, whenever the plunger comes in contact with the cartridge and tears the paper, so that the heated air may come in contact with the powder. The explosion of the powder elevates the ham-mer,and the recoil of the cylinder forces the pile into the ground. When the car tridges are thrown at the rate of fifty per minute, the hammer is operated without the use of the lever, except when desiring to cease operating. The object of the air cushion, at the top, formed by the bore in hammer, H, and piston, I, is to prevent a heavy charge from injuring the machine. The powder employed is of the most simple character, be- ing composed of one and a half parts chlorate of potash, and one part of bituminous coal, both pulverized and mixed through an ordinary sieve. This powder burns very slow in the open air; a barrel full might be ignited at once without causing any report. The charges of powder are exceedingly small, a charge of one third of an ounce being employed to throw a hammer of six hundred and seventy-five pounds weight, and it exerts a force on the head of the pile equal to a dead weight of three hundred thousand pounds for a temporary period. The pressure is exerted on the head of the pile during the presence of the plunger in the cylinder; this gives a blow and pressure of the character of the hydraulic press, with the rapidity of the hammer; hence the pile can be driven more rapidly, and forcibly, and firmer, without in any way injuring or splintering it, as in the common method of driving. The usual wrought iron ring, secured to the head of the pile, preparatory to driving, is,in this method.entirely dispensed with; and it is estimated* that even this trifling advantage will nearly pay for the powder employed. Piles can now be driven so rapidly as to constantly employ a steam engine in pulling to and hoisting the piles in position. It is believed that it will take fifty per cent less piles, when driven in-tlii3 manner, as the pile is not shattered by riveting blows which destroy the strength of the wood.nor is it vibrated (like a piano string),throughout its length, by sudden raps which destroy, to a great extent, the lateral adhesion. A Committee of Engineers, composed of W. W. Wood, Chief Engineer of IT. S. Navy, H. L. Hoff, of the Eagle Iron Works, Philadelphia, and T. J. Lovegrove, Inspector of Steam Boilers, Philadelphia, appointed to investigate the operation of this invention, give the most flattering report, indorsing fully all of the above statements. It is also recom-mended.in the highest terms.by no less than twenty-seven gentlemen, engineers of note, presidents of railroads, etc., who have seen it in operation, and confirm its great superiority to all other methods of pile driving. Any further information may be obtained by addressing Gunpowder Pile-driving Co., 505 Minor St., Philadelphia, Pa. Remarkable Mirage in the English Channel Mr. John A. Parnell, F.R.A.S., communicates to the Philosophical Magazine, an account of a remarkable mirage which occurred in the English Channel, April 13th, about 2 P.M. During the morning, and up to two o'clock, P.M., a dense fog had hung over the sea; but, apparently it was not very deep, as the sun's rays penetrated it pretty freely. At the hour above mentioned, the fog opened toward the southeast, disclosing the cliffs on the French coast; and, in the course of a few minutes, the fog had disappeared, leaving the atmosphere in a state of unusual transparency. The French clifis were apparently so lof ty,and,with every indentations clearly visible, that one miglit easily have imagined that they were but ten miles distant. On examining the objects in view through a small telescope, with a 25-power, it was at once apparent that this arose from something more than common looming. The French coast could be seen from near Calais, toward the east, far away, and many miles beyond Boulogne, toward the southwest; the land in the latter direction being ordinarily invisible, as it is situated below the horizon. Immediately under the erect image of the coast was an inverted one of about double the hight of the former. The light-house at Cape Gris-nez gave five images in a vertical line, the lowest erect, but somewhat magnified; above -that, and separated from it a pair of images of the center and highest portion of the building only.one erect and the other inverted; and over these another pair, the inverted image being like the former one, but the erect image showing the whole building. Over Boulogne, in the air, were two images of the double funnels and the mast of a tug boat, the lower image being erect and the upper inverted, the two lines of smoke bending, the one upward and the other downward, and both toward the west, till they joined together. The only tug-boat near Boulogne, at the time, so far as could beascertained.was in the harbor. The cathedra] was plainly visible, bu1 only gave a single image, Toward the southwest, beyond the French coast, some fishing luggerE were observed.hull down so that the position of the horizon could be ascer tained; over these were pairs of images of vessels which, ordinarily, woulc have been invisible. In some instances three and even four pajrs c0ld be observed placed in a vertical line, the lower image in each pair being inverted. With the exception of the uppermost pair,the imaget seemed to represent the maintop gallant sail only, and that con siderably elongated; but the highest erect image showed the mizen and the fore masts and the jib, but in no instance could the hulls be seen. The inverted images were about twice the hight of the erect. Soon after three o'clock vessels betweei the observer and the horizon began to be affected. The Vanii light ship,about 8i miles from the English coast,had her mast flagstaff, and stanchions elongated to some three times thei] proper length; this effect lasted for about ten minutes, wher they shrank to less than half their usual size, and the hul! began to rise till it was nearly as high as it was long, ant formed a most conspicuous obj ect.even to the naked eye. Upoi looking toward Dover, the pier seemed completely disorgan, ized; it appeared to be divided in half, longitudinally, witl the sea in the midst, and the stone coping moved as if hugf wavea were agitating it. At four o'clock the phenomena ceased