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repeats that the use of high-pressure steam expansively was intro- 

 duced by Mr. Woolf, and not by Capt. Trevithick. 



I had prepared a reply to this, but the editor of the Phil. Mag. 

 (Mr. John Taylor's brother) has neither permitted it to appear ac- 

 knowledged its receipt, nor noticed a second request that I might be 

 allowed a hearing. It had appeared to me desirable to terminate the 

 discussion in the same journal in which it had originated ; but as 

 this is not permitted me, allow me to crave a page in yours for my 

 explanation. 



The first attempt to draw general attention to the high duty of 

 reciprocating engines in this county was made by me (Edinburgh 

 Journal of Science, IX. 152, and X. 34.), and I have never since re- 

 sumed the subject, but to correct the inaccuracies of Mr. Taylor and 

 others. In the first of these communications I attempted a discus- 

 sion of the quantity of water evaporated, of the heat disengaged by 

 the combustion of a bushel of coals, of the utility of the steam-case, of 

 the quantity of heat passing to the chimney, and of the increased 

 elasticity of steam obtaining from a given increase of heat, when out 

 of contact with water. 



Now, Mr. Taylor, when charging me with " indulging in disputes 

 about the originators of an idea," &c, should have recollected that 

 he has himself done nothing else on this subject. Moreover, as Dr. 

 Henry justly observes, the merit of an improvement is too often its 

 ** originator's" only reward. 



In the brief historical introduction to the second of these papers of 

 mine, I have shewn that we are indebted to Captain Trevithick for 

 our improved cylindrical boilers, and for any advantages derived from 

 the use of steam of great elastic force ; to Mr. Woolf for improve- 

 ments in the workmanship and nice adjustment of the parts of the 

 engines, which had deteriorated after Mr. Watt had left Cornwall ; 

 and to Captain Grose fpr the advantages of covering all the vessels 

 which contain dense steam with thick coatings of substances which 

 transmit heat very slowly, which, however, was contemplated, and to 

 some extent realized, by Mr. Watt. 



I repeat, that Captain Trevithick^"/ - *? used high-pressure steam ex- 

 pansively in one cylinder ; is Mr. Taylor prepared to deny it ? I also 

 repeat, that Mr. Watt Jirst applied a rotatory motion to a single en- 

 gine working expansively; will Mr. Taylor "dispute" it? For, 

 notwithstanding his last (Phil. Mag., VIII. 136.) says " it must 

 be evident that it was no part of my object to discuss whether the 

 engine which I described was new or otherwise," his first paper 

 (Phil. Mag., VII. 3G9.) is entitled " on a new Rotative Steam-en- 

 gine." 



On the origin of the use of high-pressure steam expansively, Mr. 

 Taylor observes (Phil. Mag., VIII. 137.): — " I have, in another 

 place, recorded Captain Trevithick's engine at Wheal Prosper, and 

 so far done him justice ; but this engine did only about 2(5 millions 

 duty, and did not equal oilier engines then working in the com- 

 mon may." On turning to Mr. Taylor's " Records of Mining" (pub- 

 lished in 1K2 ( .)), in which, 1 presume, this act of '-'justice" was per- 

 formed, I find, under date 1813, '.' In the early part of this year, the 



