332 Dr George Wilson on the Early Hiatory of the 



self-acting valves in the cylinders and pistons, and with 

 piston-rods suspended at opposite ends of a cord passing over 

 a pulley. 



1704. The combination of the rack and pinion of the first 

 and second air-pumps, with the two barrels, twin-pistons, 

 and self-acting valves of the third. 



I proceed to justify those dates and descriptions, and to 

 consider the authors of the several improvements. As it 

 elucidates the subject under discussion, it is desirable to 

 notice, that Otto von Guericke devised his machine, the 

 earliest of all air-pumps, in 1654. The fame of his experi- 

 ments soon reached England, and interested no one there 

 so much as Boyle. He had been meditating, like Guericke, 

 on Torricelli's results, and was considering how a vacuum 

 might be best produced on the large scale, when he learned 

 that he had been anticipated. He would likely have suc- 

 ceeded in his schemes ; and the probability of this, along 

 with the certainty that Boyle had endeavoured to construct 

 an air-pump before 1659, has led Professor Robison, in his 

 article on Pneumatics, in the Encyclopsedia Britannica, to 

 claim for Boyle the merit of being an independent, though 

 not the first inventor of the air-pump. " Boyle," he says, 

 *' invented his air-pump, and was not indebted for it to 

 Schottus's account of Otto Guericke' s, ptiblished in the Me- 

 chanica Hydrauto-Pneumatica of Schottus in 1657, as he 

 asserts, Technica Curiosa^'"^ This is certainly compliment- 

 ing Boyle at Guericke' s expense, in an uncalled-for way. 

 The former, who was eminently free from envy, meanness, 

 or jealousy, explicitly declares, in the account of his own 

 first pneumatical engine, that he did not set about the con- 

 struction of an air-pump till he had heard of Guericke's 

 " way of emptying glass vessels by sucking out the air at the 

 mouth of the vessel."! 



Encouraged by the report of Guericke's success, Boyle 

 called in the assistance of Greatrex, a well-known London 

 instrument-maker of the time, whose name frequently occurs 



* Encyclopaedia Britannica, 7th Edition, Art. Pneumatics, p. 72. 

 t New Experiments, Physico-Mechanical, &c., &c. Reprinted in Birch's Bojle, 

 edition 1772, vol. i., p. 6. 



