Theory of the Bellows. Qt* 



tity of air into the cistern. To require less leather in the construc- 

 tion of the cistern, and still have the blast longer and equally pow- 

 erful ; its cover may be made so small that it will sink as far below 

 the fixed top of the cistern, as when full it would be raised above : 

 this to a certain degree would compensate for a larger sized cistern. 

 To increase the pressure, the bottom of the cistern and its cover can 

 be connected by strong spiral wires, while the blast through the pipe 

 can be governed by a regulating screw, which can be made to close 

 the whole aperture air tight, or any part. Having now described the 

 compression bellows, 1 will proceed to Air Pump. 



describe the exhaustion or air pump bel- j|:^|!iiini:;inr>„i.T:i!irii|iri':' 



lows. A represents a cistern four feet |ii ^ 



square, made air tight, of firm timber, ^ ijl 



which is to have the air in the inside of |j7 ^::;:!ii:::::'j_^:i!fe!|K 



it exhausted or drawn out. n, r repre- A ^^ ^ ***^^L 

 sent two strong light valves which are 



to open out on the under side of the cistern, near to the sides a, h. 

 These valves must open but a little way. m, m represent a strong 

 board four feet long, two wide, and so bent in its middle, where it is 

 movably and strongly hung to the bottom of the cistern A, directly 

 under the valves n, r, so that by alternately raising and depressing 

 its handle ^, it will close flat on the bottom. Two valves c, rf, are 

 to be hung in this board, immediately under those in the cistern, 

 which are to open as far outwards, and then the sides of this board 

 are to be fastened air-tight all around, by leather to the bottom of 

 the cistern, so as to allow the balancing motion, by moving the han- 

 dle A, upwards and downwards, and will exhaust as much by an up- 

 ward as by a downward motion. The operation of the valves in a 

 compression bellows, is the reverse of those in the exhaustion ; the 

 shape and dimensions are as variable. This balancing principle is 

 applicable to water as well as air in compressing and exhausting it. 

 The exhaustion bellows can be applied, with very little inconvenience, 

 10 exhaust cisterns or reservoirs of any shape or size. 



P. S. Since writing the above, I have tried the " principle" there 

 explained experimentally. The air cistern was conical, five feet at 

 top, four and a half at bottom, in diameter, and two high. The cov- 

 er was four feet in diameter, and made by means of leather to play 

 up and down in the inside of the air cistern. The balancing board 

 or its two wings, which are hung angling together, and movably hung 



