Air -Pump in England. 343 



construction." So general a statement in a brief popular 

 treatise, would not in itself, perhaps, call for criticism. It 

 is quoted, however, with approbation, by Mr Weld, and has 

 contributed, along with other things, to mislead him into a 

 curious error already referred to, which, if uncontradicted, will 

 propagate a grave mistake. The point of Professor Powell's 

 statement, lies in the word " nearly ^ In my judgment, he 

 uses it with much too great a latitude, as Mr Weld's inter- 

 pretation of its significance shews. Boyle's two pneumatical 

 engines, were single-barrelled, awkward in construction, and 

 without self-acting or mechanical valves. They could not be 

 wrought swiftly, and they produced only an imperfect vacuum. 

 Boyle himself ingenuously and ungrudgingly acknowledges 

 that Guericke's pumps exhausted better than his. In com- 

 pliment to his beautiful Pneumatic Researches, the whole of 

 Europe, designedly passing by the prior claims of the Burgo- 

 master of Magdeburg, called the air-pump vacuum. Vacuum 

 Boylianum. Boyle accepted the name, not as a compli- 

 ment, but as a designation of what he intended, when he 

 used the word vacuum in his treatises. It referred to some- 

 thing between an absolute plenum and an absolute vacuum. 

 It approached to the latter, but fell short of it. It was not 

 Nature's vacuum, the thing which she so much abhorred, but 

 Boyle's vacuum, the best which the Honourable Robert Boyle 

 could produce with his pneumatical engines. 



A merit which Boyle so modestly yet earnestly disclaims, 

 no one else need assert for him. His praise is not to have 

 constructed a perfect air-pump, or to have devised one 

 rivalling in excellence the instruments of the present day, but 

 to have made an admirable use of a very imperfect air-pump. 



The particular claim, then, set up for Boyle, that he de- 

 vised the double air-pump, implied in the general claim, that 

 he reduced the instrument nearly to its present construction, 

 may be set aside without further notice. That merit is dis- 

 claimed by himself, and ascribed by him to Papin. Hooke 

 and Hauksbee are claimants against Papin, not against Boyle. 

 Professor Robison ascribes the invention of the double pump 

 apparently to both of the former, yet, after all, decidedly to 

 neither. In one place he states that Boyle ** was now assisted 



