405 Additional Nofe^. 



and, consequenUy, the engine can act with exactly the necessatr/ 

 degree of energy. 



" Ivlr. "Watt gained a patent for his engine in 1 7^8 j but the 

 further prosecution of his designs \^'as delayed by other avocations 

 till 1775, \vhen, hi conjunction with Mr. Boulton, of Soho, near 

 Birmingham^ numerous experiments were made, on a large scale^ 

 by their united ingenuity, and great improvements added to the 

 machinery, and an act of parliament obtained for the prolongation 

 -of their patent for twenty-five years : they have, since that time, 

 drained many of the deep mines in Cornwall, v.hich, but for the 

 happy union of such genius, must immediately have ceased to 

 ^^ ork. One of, these engines works a pump of eighteen inches 

 diameter, and upwards of a hundred fathom, or 6OO feet high, at 

 the rate of ten or t^^-clve strokes, of seven feet long each, in a 

 minute, and that with one fiftli part of the coals which a common 

 engine would have taken to do the same work. The power of 

 this engine may be easier comprehended, by saying, that it raised 

 a weight equal to 81000 pounds, eighty feet high, in a minute, 

 which is equal to the combined action of two hundred good 

 horses. In Newcomen's engine this would have requued a cylin- 

 der of ihe enormdus diameter of 120 inches, or ten feet; but as 

 rn this cno i«e of Mr. Watt and Mr. Boulton the steam acts, and a 

 vacuum is made, alternately abo\'e and below the piston, the 

 •power exerted is double to what the same cylinder "Vvould other- 

 ways produce, and is further augmented by an inequality in th« 

 length of the two ends of the lever. 



** These gentlemen have also, by other contrivances, applied 

 their engines to the turning oi\mills for almost every purpose, of 

 \^hich that great pile of machinery, the Albion Mill, is a well- 

 known instance. Forges, slitting-mill^, and other great works, 

 are cri'cted where nature has furnished no mnning water, and fu- 

 lul-e times may boast that this grand ajid useful engine was in- 

 vented and perfected in our own countr}'." — Botanic Garden, 

 Part i. Additional JS'o/c XI. 



jN'o/r CO)y p. 64. — It appears that Bollond was not the first per- 

 son who invented Jlchrmnatic glasses. As early as 1729, Chestei* 

 More ILill, esq., of Mort-HuU, m the county of Essex, as 

 appears by his papers, considering the different humours of the 

 eye, imagined they M-ere placed so as to correct the different 

 refrangibility of liglit. He tlien conceived, that if he could find 

 ^ubsiiuices having such properties; as he supposed these huniDun 



