2L3 



Society. Mr Weld, therefore, is certainly mistaken in conceiving 

 tiiat the old double-barrelled pump in the Society's possession is 

 Boyle's original air-pump. It is probably not an instrument of 

 Boyle's century. 



Dr Thomas Young also supposes the first English air-pump to 

 have had two barrels, and ascribes their introduction to Hooko. — 

 (^Natural Philosophy, Kelland''s edition, p. 278.) The latter, how- 

 ever, states distinctly, that the instrument he made for Boylo had one 

 barrel (Waller's Life of Hooke, p. iii.), and his drawing of it, which 

 is engraved in the vignette frontispiece on the title-page of the se- 

 veral volumes of Birch's Boyle, represents the great pneumatical en- 

 gine as possessing but one cylinder. Professor Robison, in his trea- 

 tise on Pneumatics, ascribes the double pump in one place to Hooke 

 (jBmc. Brit., 7th Ed., p. 80), and in another to Hauksbee (p. 93). 

 Professor Robison does not refer to any writing of Hooke' s as con- 

 taining a claim, on his part, to the invention in question ; and it is 

 impossible to suppose that Hooke could have constructed a double 

 air-pump before Papin did, without Boyle being aware of the cir- 

 cumstance. At all events, till it is shewn that Hooke himself claimed 

 the double air-pump as his invention, it is unnecessary to discuss his 

 supposed merits as its inventor. 



Hauksbee appears to have been the first Englishman who con- 

 structed an air-pump with two barrels. He described it in his Trea- 

 tise entitled " Physico-Mechanical Experiments on various subjects, 

 byFrancis Hauksbee, F.R.S., 1709." It was constructed in, or about, 

 1704, so that it cannot come into competition with a double air-pump 

 of Hooke's invention (if he ever devised one), seeing that he died in 

 1702. Still less can it supplant Papin's instrument, which was 

 brought to England in 1676, and must have been known to Hauks- 



|bto. 



Hauksbee's air-pump was a combination of the rack and pinion of 



[Hooke's pneumatical engine which he constructed for Boyle, and the 

 two barrels, twin pistons, and self-acting valves of Papin's pump. 

 From all, it appears, that no English claimant, at least, can dis- 



Ipute priority, so far as the double pump is concerned, with Papin. 



[Winkler, who was Professor of Natural Philosophy at Leipsic in 



ithe middle of last century, in his Sketch of the History of the Air- 

 ^ump, I'efers to Hauksbee's as the first constructed with two barrels. 

 -{Elements </ Natural Philosophy, 1757. English Translation, 



