Air-Pump in England. 853 



of later date than 1703, after which we may date the pump 

 also. It is not unimportant to notice, that it was not made 

 public, and probably not constructed, till after Hooke's death. 

 Hauksbee speaks of it as an improvement on Boyle'*8 air- 

 pump. Whether he is to be understood as referring to Pa- 

 pin's machine, does not appear ; but if familiar with Boyle's 

 descriptions of air-pumps, he could not be ignorant of Papin's. 

 At all events, Hauksbee' s pump (the long gauge excepted) is 

 simply Papin's, with the stirrup arrangement and pulley, re- 

 placed by racks on the piston-rods, and a pinion, moved by a 

 handle. The advantages which attend the employment of 

 two barrels, with their pistons balanced against each other, 

 so as to be nearly indifferent to the pressure of the atmo- 

 sphere, are dwelt upon at great length, as if they had been 

 realised in Hauksbee*s ins^truments for the first time. All 

 those advantages, however, are pointed out with as much 

 distinctness in the description of Papin's instrument of 1676. 

 In truth, the excellence of Hauksbee' s pumps, did not lie, as 

 Professor Robison thought, in the introduction of any new 

 principles (the long gauge excepted), but in the combination of 

 recognised principles, and in the nicety of the mechanical con- 

 struction of the pumps. They were a happy union of the 

 best peculiarities of Papin and Hooke's air-pumps. Hauksbee 

 adopted the double barrel, counterbalancing pistons, and 

 self-acting valves of Papin ; but replaced his awkward stir- 

 rups and i>ulley, by Hooke's rack and pinion. I am strongly 

 inclined to believe that Hooke*s supposed invention of the 

 double barrel, has originated in the observation of his rack 

 and pinion in most modern air-pumps. It should seem, 

 however, according to the evidence hitherto produced, that 

 Hauksbee, not Hooke himself, first applied the latter's de- 

 vice to the double air-pump. Nevertheless, Hooke is en- 

 titled to be named in connexion with his own ctmtrivance, 

 and thus he will have a three-fold connexion with the in- 

 strument, as deviser of the first air-pump, as one of the de- 

 visers of the second, and as the author of the method of rais- 

 ing and depressing the pistons in the fourth. Yet it cannot 

 be denied, that the great merit of the early double pump does 

 not consist in the mode, whatever it be, employed to moYe 



