WITH NOTES. 423 



timber made engines are light, and their &quot; materials to 

 be found everywhere.&quot; 



Then the gun-powder is costly; a a whole Cannon 

 requiring for every charge 40 pound of powder, and a 

 bullet of 64 pounds,&quot; and in proportion for lesser can 

 non ; whereas those other engines may be charged only 

 with stones. So that only for the superior force of 

 cannon &quot;those ancient inventions&quot; he conceives to be 

 44 much more commodious than these later inventions.&quot; 



Among questions propounded and agreed upon, in 

 January, 1660, to be sent to Teneriffe by the Lord 

 Brouncker and Mr. Boyle, the fifth was, 44 Try the 

 power of a stone bow, or other spring, both above and 

 below (the hill), and note well the difference.&quot; Weld s 

 Hist. Eoyal Society, Vol. i. p. 98. 



25. 



How to make a Weight that can 

 not take up an hundred pound, and 

 yet fliall take up two hundred pound, 

 and 6 at the felf-fame diftance from 

 the Centre ; and fo proportionately 

 to millions of pounds. 



8 and omitted. 



[A double-drawing Engine for weights^] The articles 

 Nos. 25, 27, and 29 can only be taken as descriptive 

 of elucidatory models, demonstrative of the applica 

 tions of a certain principle, the result of condensa 

 tion. For some unaccountable reason there has 

 been a prevalent opinion that the Marquis was ignorant 

 of condensation. If such an opinion is grounded on 

 his not expressly alluding to it in the 44 Century,&quot; then 

 by the same rule it might be doubted whether he 



