AND SURFACE CONDENSER. 319 



strncted, \vas again on his return giving his whole 

 thoughts to the idol of his life. 



During that period scientific men in Europe thought 

 and wrote much on the question of relative temperature, 

 pressure, economy, and manageability of steam. New- 

 comen's great discovery a century before was the 

 avoidance of the loss of heat by the cooling at each 

 stroke of the exterior of the steam-vessel of Savery's 

 engine by injecting cold water into the steam in the 

 cylinder. After fifty years came the Watt improve- 

 ment, still reducing the loss of heat by removing the 

 cold injection-water from the steam-cylinder to a sepa- 

 rate condenser. 



The high-pressure steam-engine was perfect without 

 injection-water, though when convenient its use was 

 equally applicable as in the low-pressure engine. 

 Trevithick, on his return to civilized life, read the 

 views of Watt on steam, as given in * Farey on the 

 Steam-Engine.' On informing Davies Gilbert of his 

 doubts of the accuracy of those views, and of his inten- 

 tion of testing them by comparison with the work 

 performed by Cornish pumping engines, his friend, who 

 had just published his 'Observations on the S team- 

 Engine,' 1 forwarded a copy, from which the following 

 is an extract : 



" One bushel of coal, weighing 84 Ibs., has been found to 

 perform a duty of thirty, forty, and even fifty millions, aug- 

 menting with improvements, chiefly in the fire-place, which 

 produce a more rapid combustion with consequently increased 

 temperature, and a more complete absorption of the generated 

 heat ; in addition to expansive working, and to the use of steam 

 considerably above atmospheric pressure." 



1 L < >lis<Tv;it:ons on the Sh-am- Engine,' by Davies Gilbert, V.1M..S., January 

 25th, 1827. Sec ' Philosophical Transactions.' 



