atmo sphere. various directions. The air being thus separated from the water, ascends into the upper part of the vessel, and rushes through the opening F, whence it is conveyed by the pipe FG to the fire at G, while the water falls to the lower part of the vessel, and runs out by the openings M, N. In order that the greatest quantity of air may be driven into the vessel DE, the water should begin to fall at C with the least possible velocity; and the distance of the lowest tubes o, p, from the extremity of the pipe H should be to the length of the vertical tube CH as 3 to 8, in order that the air may move in the pipe FG with sufficient velocity. The part of the tube between op and H, and the vessel DE, must be completely closed, to prevent the escape of the internal air. The wind is supplied Fabri and Dietrich imagined that the wind is from the occasioned by the decomposition of the water, or its transformation into gas, in consequence of the agitation and percussion of its parts. But M. Venturi,' to whom we are indebted for the first philosophical account of this machine, has shewn that this opinion is erroneous, and that the wind is supplied from the atmosphere; for when the lateral openings m, n, o, p, were shut, no wind was generated. Hence the principal object in the construction of these machines is to combine as much air as possible with the descending current. With this view the water is often made to pass through a kind of cullendar placed in the open air, and perforated with a great number of small trian Experimental Enquiry concerning the lateral communication of motion in Fluids. Prop. &. gular holes. Through these apertures the water descends in many small streams, and by exposing a greater surface to the atmosphere, it carries along with it an immense quantity of air, and is conveyed to the pedestal P by a tube CH, open and enlarged at C, so as to be considerably wider than the end of the pipe which holds the cullendar. It has been generally supposed that the waterfall should be very high; but Dr. Lewis has shewn, by a variety of experiments, that a fall of 4 or 5 feet is sufficient, and that when the height is greater than this, two or more blowing machines may be erected, by conducting the water from which the air is extricated into another reservoir, from which it again descends and generates air as formerly. That the air, which is necessarily loaded with moisture, may arrive at the furnace in as dry a state as possible, the condensing vessel DE should be made as high as circumstances will permit; and in order to determine the strength of the blast, it should be furnished with a gage a b filled with water. Franciscus Tertius de Lanis observes, that he has seen a greater wind generated by a blowing machine of this kind, than could be produced by bellows 10 or 12 feet long. the rain The rain wind is produced in the same way as Cause of the blast of air in water-blowing machines. When wind. the drops of rain impinge upon the surface of the sea, the air which they drag along with them often produces a heavy squall, which is sufficiently strong to carry away the mast of a ship. The 2 Wolfius makes the length of the tube C H 5 or 6 feet Opera Mathematica, tom. i, p. 830. In Magisterio Naturæ et Artis, lib. v, cap. 3. Vol. II. Dd same phenomena happens at land, when the clouds empty themselves in alternate showers. In this case, the wind proceeds from that quarter of the horizon where the shower is falling. The common method of accounting for the origin of winds by local rarefactions of the air, appears to me pregnant with insuperable difficulties; and I am apt to think, that these agitations in our atmosphere, ought rather to be referred to the principle which we have now been considering.+ 4 Those who wish for more information upon the subject of water-blowing machines, may consult Lewis's Commerce of Arts; the Journal des Mines, N° 91; or Nicholson's Journal, vol. xii, p. 48. HYDRAULICS. DESCRIPTION OF WHITEHURST'S MACHINE FOR RAISING WATER BY ITS MOMENTUM; AND MONT- its momen Mr. White THE HE ingenious idea of raising water by the mo- The idea of mentum of the water itself was first suggested by raising by Mr. Whitehurst in the Philosophical Transac- tum sugtions for 1775. The same principle, in an im-gested by proved form, has lately been revived in France, hurst. and has excited considerable attention both on the continent and in this country. Whatever credit, therefore, is due to the inventor of the hydraulic ram, properly belongs to our countryman Mr. Whitehurst, and Montgolfier can lay claim to nothing more than the merit of an improver. of Mr. chine. Mr. Whitehurst's machine, which is represent- Description ed in figure 2a of Plate XIV, was actually erect-whiteed at Ŏulton in Cheshire, and completely an-hurst's maswered the expectation of its inventor. AM is PLATE the original reservoir, whose surface is on a level XIV, with B, the bottom of the reservoir BN. The Fig. 2.App. main pipe AE, is 1 inches diameter, and nearly two hundred yards long, and the branch pipe EF is of such a size, that the cock F is about of Mont ram. 16 feet below the surface M of the reservoir. D is a valve box, with its valve a, and C is an air vessel, into which are inserted the extremities m, n, of the main pipe, bent downwards to prevent the air from being driven out when the water is forced into it. Now, since the difference of level between the cock F, and the top of the reservoir AM is 16 feet, upon opening the cock F the water will rush out with a velocity of nearly 30 feet per second. A column of water, therefore, two hundred yards long, is thus put in motion, and, though the aperture of the cock F be small, it must have a very considerable momentum. Let the cock F be now suddenly stopped, the water must evidently rush through the valve a into the air vessel C, and condense the included air. This condensation must take place every time the cock is opened and shut, and the included air being highly compressed, will press upon the water in the air vessel, and raise it into the reservoir B N. Description From this brief description of Whitehurst's golfier's engine, the reader will easily perceive its resemhydraulic blance to that of Montgolfier, a section of which is represented by figure 3. Ris the rePLATE XIV, servoir, RS the height of the fall, and ST the Fig. 3. App. horizontal tube which conducts the water to the engine ABHTC. E and D are two valves, and FG a pipe reaching within a very little of the bottom CB. Now let water descend from the reservoir, it will rush out at the aperture m n till its velocity becomes so great as to force up the valve E. The water being thus suddenly checked, and unable to find a passage at mn, will rush forwards towards H, and raise the valve D. A portion of water being admitted into the vessel AB C, the impulse of the column of |