Air-Pump in England. 351 



have failed to become acquainted with it, through one or 

 more of his large circle of friends and acquaintances. Boyle, 

 however, who acknowledges his obligations to Hooke's inge- 

 nuity, in reference to the second as well as to the first air- 

 pump, speaks of Papin's double barrel as something quite 

 new to him, and extols its advantages. If Hooke, there- 

 fore, constructed a double pump, it must have been of later 

 date than Papin's machine, with which he certainly was ac- 

 quainted. It was Hooke who introduced Papin to the Royal 

 Society, May 22, 1679.* They were associated in the con- 

 ducting of the correspondence of the Society, and must have 

 been much together.t In the report of the Society's meet- 

 ing for July 17, 1679, it is stated that " the second experi- 

 ment of Mr Hooke was with the exhausting engine of Mon- 

 sieur Papin. "J Unless, therefore, it can be shewn, that 

 Hooke preceded Papin in the construction of a double-bar- 

 relled air-pump, the latter is plainly, and with consent of the 

 former, entitled to the entire merit of priority. Hooke did 

 construct two pneumatical engines before he became ac- 

 quainted with Papin's machine, but they had no resemblance 

 to it. The one was a condensing engine, of which a minute 

 description is not given. § Its consideration is foreign to my 

 present purpose. The other was a very curious machine, 

 which has escaped the attention of the historians of the air- 

 pump. It is referred to by Birch, in his History of the 

 Royal Society, as " anew way of making a vessel for extract- 

 ing the air, so large that a man might sit in it." || Hooke 

 thus described it : " It consisted of two tuns, one included in 

 the other ; the one to hold a man, the other filled with water 

 to cover the former, thereby to keep it stanch ; with tops to 

 put on with cement, or to take off; one of them having a 

 a gauge, to see to what degree the air is rarefied ; as also a 

 cock, to be turned by the person who sits in the vessel, ac- 

 cording as occasion shall require."1[ This instrument was 



* Birch's History of Royal Society, vol. iii , p. 486.- 



t Op. cit., vol. iii., p. 491. X Ibid., p. 497. 



§ Ibid., vol. i., p. 125. II Ibid., vol. ii^ p. 468. 



f Ibid., p. 467. 



