344 Dr George Wilson 07i the Early History of the 



by Dr Hooke.'' " This person made a great improvement on 

 the air-pump, by applying two syringes/' &c.* .Professor 

 Robison then goes on to describe an instrument identical 

 with Papin's in the arrangement of its valves, and constructed 

 on similar principles. Instead, however, of the stirrups con- 

 nected by a cord passing over a pulley, the pistons are raised 

 and depressed by a pinion or cogged wheel, working into 

 racks cut on the piston-rods, as the single piston was moved 

 in Boyle's pneumatical engines. No date is assigned to this 

 alleged invention of Hooke' s, nor does its describer quote or 

 name any work in justification of his statement Professor 

 Robison then describes Hauksbee's pump, which is almost 

 identical with the instrument attributed to Hooke, except that 

 it is provided with the former's well-known gauge, an appen- 

 dage which measures, but at the same time diminishes rather 

 than increases the rarefying power of an air-pump. Through- 

 out the remainder of his treatise Robison refers to Hooke and 

 Hauksbee as if they had been independent inventors of the 

 double pump, the priority, however, being given to Hooke ; 

 yet, in concluding his historical sketch, the latter's name is 

 omitted, and the author, as if he preferred Hauksbee's claim, 

 says : " the double barrel and gauge by Hauksbee were capi- 

 tal improvements, and on principle.''! 



Dr Thomas Young, generally so exact, is not more accu- 

 rate than Professor Robison. " In the year 1658,'' says the 

 f( rmer, " Hooke finished an air-pump for Boyle, in whose 

 laboratory he was an assistant. . . . Hooke's air-pump 

 had two barrels.''^ Dr Young, a rare thing with him, gives 

 no authority for his statement ; and he evidently supposes 

 that the first English air-pump of 1658 was a double-barrelled 

 one. I have already, however, pointed out sufiiciently fully, 

 that 1658 or 1659 is the date of Boyle's great pneumatical 

 engine, which Hooke constructed for him, a single-barrelled 

 pump, with a globular receiver directly attached to it. 



Erroneous as Dr Young's statement certainly is, it appa- 



* Enc. Brit., 7th Ed., Art. Pneumatics, p. 80. 



t Op. cit., p. 93. 



X Young's " Natural Philosophy," edited by Kelland, p. 278. 



