212 



height, that the pistons might move air-tight in them. From the 

 Cylinders, tubes passed to a common canal, terminating in the air- 

 pump plate, on which receivers to be exhausted were laid, as in 

 Boyle's second engine. 



It is not a little singular that Papin's machine should have been 

 ovei'looked by most later writers. It is not referred to in any recent 

 English work of authority, although its curious stirrup arrangement, 

 which has been employed in no English air-pump, might have been 

 expected to direct attention towards it. Papin is mentioned inci- 

 dentally by Nairne as an improver of the air-pump. — {Phil. Trans,, 

 ^111, p. 635.) Dr Hutton, in his Mathematical Dictionary (vol. i., 

 p. 55, 1796), mentions Papin's two barrels and twin pistons, but 

 not the stirrup arrangement. In Shaw's abridged Boyle, the whole 

 machine is described and figured, but Papin's name is not mentioned. 



Recent writers on Pneumatics having overlooked Papin's machine, 

 whilst they universally acknowledge the importance of two baiTels 

 with the pistons counterbalancing each other, have attributed this 

 great improvement to Boyle, to Hooke, or to Hauksbee. 



Boyle's imputed claim to the honour of having first constructed 

 a double-barrelled air-pump, may be summarily dismissed, as he him- 

 self disavows the honour, refers to Papin's air-pump as new to him, 

 and ascribes its invention to Papin. — [Birch's Boyle, vol. iv., p. 506.) 

 Mr Weld, however, puts Boyle's claim on another, and at first sight 

 apparently satisfactory, basis. The Royal Society, according to the 

 former, who is its assistant-secretary, possesses Boyle's oi-iginal air- 

 pump, which has two barrels, and otherwise much resembles an air- 

 pump of the present day. — [History of Royal Society, vol. i., p. 96,) 



If, however, the instrument shewn to visitors to the Royal So- 

 ciety's apartments, be the earliest English air-pump, then Boyle was 

 not only the first to employ a double-barrelled pneumatic pump, but 

 his earliest pneumatical engine had two barrels. The instrument, 

 however, which, as Boyle informs us (" Continuation of New Expe- 

 riments, &c., on the Spring and Weight of the Air," Oxford, 1669, 

 Pi'eface), he gave to the Royal Society, in 1662, was his " Great 

 Pneumatical Engine," which he described and figured in 1659. It 

 had a single barrel, and was quite unique in its construction and 

 appearance. The first double-barrelled air-pump to which Boyle re- 

 fers is Papin's, with which he did not become acquainted till some 

 seventeen years after he presented his earliest air-pump to the Royal 



