462 Additional Notes. 



" To prevent the cooling of the cyHnder hy the contact of 

 the external air, he surrounded it with a case containing steam» 

 which he again protected by a covering of matters which 

 conduct heat slowly. 



" This construction presented an easy means of regulating 

 the power of the engine, for the steam being the acting 

 power, as the pipe which admits it from the boiler is more 

 or less opened, a greater or smaller quantity can enter during 

 the time of a stroke, and, consequently, the engine can act 

 with exactly the necessary degree of energy. 



" Mr. Watt gained a patent for his engine in 1768, but 

 the further prosecution of his xlesigns was delayed by other 

 avocations till 1775, when, in conjunction with Mr. Boul- 

 TON, 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, which, but for the happy 

 union of such genius, must immediately have ceased to work. 

 One of these engines works a pump of eighteen inches dia- 

 meter, and upwards of a hundred fathom, or 60Q feet high, 

 at the rate of ten or twelve strokes, of seven feet long each, 

 m a minute, and that with one fifth 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 81,000 pounds, eighty 

 feet high, in a minute, which is equal to the combined ac- 

 tion of two hundred good horses. In Newcomen's en- 

 gine this would have required a cylinder of the enormous 

 diameter of 1 20 inches, or ten feet ; but as in this engine of 

 Mr. Watt and Mr. Boulton the steam acts, and a vacuum 

 is made, alternately above and belov/ the piston, the power 

 exerted is double to what the same cylinder would otherways 

 produce, and is further augmented by an inequality in the 

 length of the two ends of the lever. 



" These gentlemen have also, by other contrivances, ap- 

 plied their engines to the turning of mills for almost every 

 purpose, of which that great pile of machinery, the Albion 

 Mill, is a well-known instance. Forges, siitting-mills, and 

 other great works, are erected where nature has furnished no 

 running water, and future times may boast that this grand 

 and useful engine was invented and perfected in our own 

 country." — Botanic Garden, Parti, p. 154. New-Yorlc edit. 



