Air-Pump in England, 345 



rently derives the fullest confirmation from the announcement 

 made by Mr Weld in his " History of the Royal Society,"* 

 that that body possesses a double-barrelled air-pump, pre- 

 sented to it by Boyle in 1662. This instrument is shewn to 

 visitors, and can be seen at Somerset House. Its barrels 

 are about fourteen or fifteen inches long, and the piston-rods 

 have racks working into an unusually large toothed wheel or 

 pinion moved by a handle. The whole instruuient resembles 

 an air-pump of the present day. 



It should seem at first sight impossible to question evi- 

 dence so demonstrative of the true date of the double pump, 

 as that supplied by the existence, in the Royal Society's col- 

 lections, of an air-pump presented to it by Boyle, and pre- 

 served since 1662 in its Museum. Mr Weld's statement, 

 however, will not bear examination. He has himself, with- 

 out intending it, supplied one of the means of disproving its 

 accuracy. In the first volume of his History (p. 96) he quotes 

 the following passage from the Journal Books of the Royal 

 Society: — ^^ January 2, 1660-1. — The Society again met, 

 when Lord Brouncker was desired to prosecute the experi- 

 ments of the Recoyling of Gunns, and to bring it in against 

 the next meeting, and Mr Boyle his Cylinder" 



In explanation of the last allusion, Mr Weld furnishes a 

 note. " This refers to his air-pump, which, according to 

 Professor Powell, he reduced to nearly its present construc- 

 tion. The reader will be interested to know, that the origi- 

 nal air-pump alluded to above, and constructed by Boyle, was 

 presented to the Society by him in 1662, and still remains in 

 their possession. It conaists of two barrels^ The text and 

 the annotation plainly contradict each other. Had Mr Weld 

 considered, he would have seen that an instrument empha- 

 tically called a cylinder, because provided with one barrel, 

 could not possibly be provided with two barrels. The air- 

 pump the Royal Society now possesses is not, then, the one 

 the Society requested Mr Boyle to bring to its meetings in 

 1660. Neither is it the instrument which he formally pre- 

 sented to the Society in 1661 or 1662 ; for he had not a 



* Vol. i., p. 97. 



