336 Dr George Wilson on the Early History of the 



" Rarefying Engine," and " Boyle's Cylinder ;" and it was 

 known over Europe as Machina Boyliana, Boyle's Machine. 

 Pneumatical Engine was a well-chosen name. The instrument 

 was something more than a rarefying machine, or vacuum pro- 

 ducer. It could be used to condense air into the receiver, as 

 well as to withdraw air from it, as Boyle shewed. Vapours and 

 gases could also be introduced into the globe. It was thus an 

 air, gas, or pneumatical engine. At the present day it would 

 be considered an awkwardly-contrived, ill-proportioned, and 

 imperfect instrument. It taught Boyle, however, and his 

 contemporaries so much, achieved such wonders, was so diffi- 

 cult of construction, and so costly, that he called it the Great 

 Pneumatical Engine. He did not retain it long in his pos- 

 session. With a rare and noble liberality, he presented it to 

 the Koyal Society in 1661,* so that his poorer scientific 

 brethren, who could not afford so expensive a piece of appa- 

 ratus, might prosecute pneumatics at his cost, and multiply 

 experiments with the great engine. • 



For six or seven years, accordingly, Boyle turned aside 

 from pneum^atic research, and no one took his place, at least 

 in Great Britain. Finding, in consequence, that few new 

 experiments had been made in many years, he resumed his in- 

 quiries into the properties of the air, and began by constructing 

 a new air-pump. His account of this, which he distinguished 

 as his '' second engine," and of the experiments which he 

 made with it, was first published in the shape of a letter to 

 his nephew, Lord Dungarvan, entitled "A continuation of New 

 Experiments Physico-Mechanical, touching the Spring and 

 Weight of the Air, &c. &c. ; Oxford, 1669." The letter is 

 dated (March 24) 1667, which we may consider the year in 

 which the second English air-pump was constructed, though 

 it may have been finished in the preceding year. 



Various considerations " invited me," says Boyle, " to 

 make some alterations on the structure, some of them sug- 

 gested by others, (especially by the ingenious Mr Hooke), 

 and some of them that I added myself, as finding that with- 



* Weld states that this gift was made in 1662 {History q/ Royal Society , vol. i., 

 p. 97) In Birchs History of the Society, the following entry occurs : •' IGGl, 

 May 15. — Mr Boyle presented the Society with his engine ;'" vol. i., p. 23. 



