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Hooke, who constructed for him tlie air-pump which he employed in 

 his first series of pneumatic researches. It appears to have been 

 commenced in 1658, and completed in 1659, according to the sepa- 

 rate testimony of Boyle (New Experiments, &c., touching the Spring 

 and Weight of the Air, written in 1659, published in 1660, Birch's 

 Boyle, vol. i., p. 7), and Hooke (Waller^ s Life of Hooke, p. iii.). The 

 first English air-pump, which may bo dated from 1659, had a single 

 brass barrel about 14 inches in length, and 3 in internal diameter. 

 It stood upon a strong wooden tripod, with its mouth turned down- 

 wards. The piston or sucker was solid. The shank or piston-rod 

 had teeth cut on it, so as to form a rack, and was moved by a toothed 

 wheel or pinion working into the rack, and turned by a handle, as 

 in the air-pumps of the present day. A hole was bored in the side 

 of the upper end of the cylinder, provided with a ground brass plug 

 or stopper, which could be drawn out or pushed in by the hand. 

 This was the only valve in the engine. The object of the inversion 

 of the cylinder, was to allow the globular or pear-shaped glass re- 

 ceiver, from which it emptied the air, to be placed in a vertical posi- 

 tion above the pump. 



The receiver had a large opening at the top for inserting objects 

 into it. The opening could be narrowed by a tight-fitting broad 

 brass ring, in the centre of which was an aperture provided with a 

 brass stopper to close it. The receiver terminated below in a nar- 

 row neck cemented into a brass stop-cock, which was ground to fit 

 an opening in the upper end of the cylinder, near to the valve in it. 



In using the pump to exhaust, the piston was first made to ascend 

 or driven home, whilst the valve in the cylinder was open, and the 

 stop-cock of the receiver shut. The valve was then closed by its 

 stopper or plug, the stop-cock opened, and the piston drawn down. 

 The stop-cock was then closed a second time, the valve opened, and 

 the rarefied air which had entered the cylinder from the receiver, 

 expelled from the former by the second ascent of the piston, and 

 so on ad infinitum. 



By reversing the order in which the valve and stop-cock were 

 closed and opened, the pump could be made to condense instead of 

 rarefying the air of the receiver. The valve for that purpose was 

 opened, whilst the stop-cock was shut, and the piston drawn down so 

 as to allow the cylinder to be filled with atmospheric air. The valve 



