Messrs. Russell & Co., Greenock and Port Glasgow, show at the Glasgow exhibition a very numerous and varied show of sailing models. First, we find the noble four-masted ships of from 1,800 tons to 2,200 tons, which sail and carry well on their tonnage, and which are worked by fewer hands than are required for a ship of the same burden with three masts but squarer yards. Some owners prefer the latter, and so Messrs. Russell show not only such handsome specimens as the four-masted Falls of Earn, but also the three-masted Ardencraig and Soudan. One of the favorite models of this firm is that of their 1,500 ton ship with three masts, represented by the Cromartyshire, of which type they have built a large number of vessels noted alike for their carrying capacity and their excellent sailing qualities. The Main, built for Mr. James Nourse, of London, is a good specimen of their 1,700 ton ship, as designed for the special trade of the owner, between Calcutta, Demerara, and London. Their 1,300 ton bark is represented by the model of the Aboukir Bay and her sisters of the Bay Line, owned by Messrs. Hatfield, Cameron & Co., of Glasgow; while their 1,000 ton barks are shown in the model of the Banca, belonging to Messrs. P. Denniston & Co., of the same city. These are about the smallest class of sailing ships built during recent years, the demands of the shipping trade being such as to make it unprofitable to sail anything smaller than about 1,500 tons; while the tendency is to exceed 2,000 tons in burden, and to reach even as high as 3,000 tons.—The Engineer.
WATER BLAST PUMP.
It is well known that the principle which is applied to the construction of vacuum or filter pumps, and which aims at the production of rarefied air in a certain inclosed space, may also be applied to the production of air pressure.
A simple apparatus by which this may be accomplished has recently been constructed by A. Beutell.
A tall cylindrical flask, K (see cut), is provided with an outlet tube near the bottom, and its stopper carries two tubes, one (M) for the entrance of a jet of water, and the other (L) for the exit of the compressed air, which may be conducted to a blast lamp or wherever air under pressure may be needed. The column of water entering through M causes air to be sucked in through the little hole at c, and this air, after arriving in the flask, is gradually compressed by the continuously entering water.
In order that the apparatus may work properly, it is necessary to construct the tube, M, in a particular manner, and of certain definite proportions. Fig. 3 exhibits its bore and shape in an enlarged view. A short distance below the orifice of the tube it is slightly expanded, and then gradually contracts to the place, b. It then again expands to an oblong cavity, and contracts again to a neck, e, which is a trifle wider than that at b, and which must be so situated that the column of water passing through b is exactly perpendicular to the center of the aperture at e. The tube then expands again to its original diameter, and is slightly curved, which is done to prevent any of the compressed air in the cylinder, K, from regurgitating upward.
The outlet tube at A is preferably constructed as shown in Fig. 2. Instead of being made of one piece, it is there represented as consisting of two pieces joined together by rubber tubing, a sort of check valve, G, being introduced into the rubber joint. By regulating the check valve, that is by approaching it more or less to the exit of the tube, A, the outflow of water may be regulated. It is important to adjust this so that the cylindrical flask will always be at least half full, and never over three-fourths filled. While the column of water falls through the aperture at b, into the expanded portion of M, it aspirates air through the little orifice, c, communicating with the outer air, and this air is carried along with it into the flask, where it accumulates until it is under a pressure equal to that of the column of water entering the apparatus, when the latter will cease to flow. By allowing the air to escape through L, more will be successively compressed, so that a steady blast may be obtained.
