. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 28S THE CIVIL ENGINEER AND ARCHITECFS JOURNAL. [Sept. side of the chamber, as shown by the Hotted lines, the water entering at A now flows through pipe B, but the water in pipe C having been in motion its momentum will carry it onwards in the original direction, leaving a vacuum behind ; at the same time it will be oljserved, that the port has been opened between pipe C and the condenser, and the water of condensation and vapour will rush out of the condenser into the pipe C.
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 28S THE CIVIL ENGINEER AND ARCHITECFS JOURNAL. [Sept. side of the chamber, as shown by the Hotted lines, the water entering at A now flows through pipe B, but the water in pipe C having been in motion its momentum will carry it onwards in the original direction, leaving a vacuum behind ; at the same time it will be oljserved, that the port has been opened between pipe C and the condenser, and the water of condensation and vapour will rush out of the condenser into the pipe C. On again reversing the valve D, the same effect is pro- duced in pipe B, and so on alternately. Having thus briefly explained the form and operation of the ma- chine, we have now to inquire what extent of vacuous space is likely to be ol)tained under ordinary circumstances. Let P = the weight of the cilumn of water in lbs.; G=: the co-eflB- cient of gravity ^ 32 ; V = the velocity in feet per second. P Then the vis viva of the water = — V. G Again, let A= the area of the pipe in square inches ; R =; the re- sistance due to the immersion at atmospheric pressure; L = the length of the vacuum in feet. Then we have ihe mechanical effect overcome by the water while stoppingz=: A X R X L. But this mechanical effect is equal to half the vis viva. Hence, A x R X L= i ^ x VS or L: Or PX V2 2xG XAXR. Let us now apply this formula to a particular case. Suppose the vessel to be 110 feet between the perpendiculars, and the length of the pipe to be 90 feet, diameter 0 inches; say she is propelled by one engine of 30-inch cylinder, and 3 feet stroke, then the air-pump would have a capacity of about 4,300 cubic inches. Again, take the speed of the vessel at 14 miles per hour, or 20 feet per second, then we have— A =; 28 square inches, V ^=- 20 feet per second. Hence L = P = 1092 lb. G= 32 R= 17 1092 X 20, : 14 feet 4 inches. 2 X 32 X 28 X 17 The contents of which is 4896 inches, and with
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