36 Mr Henwood's account of the 



usually made of cast-iron, and continually exposed to the in- 

 tense action of the fire, the water was frequently driven out of 

 them, and their temperature became considerably elevated ; 

 by the readmission of water at a comparatively low tempera- 

 ture, they were rapidly cooled, and the consequent contraction 

 occasioned the frequent fracture not only of the joints, but 

 also of the tubes themselves. Frequent trials demonstrated 

 their inferiority to those of Trevithick, in favour of which 

 they were soon relinquished. 

 w Previously to Mr Woolf 's coming into Cornwall, he had 

 revived Mr Hornblower"'s idea of employing the expansive 

 force of steam in a second cylinder ; and by having his en- 

 gines made and fitted together in a much more accurate man- 

 ner than had hitherto been the practice in that neighbour- 

 hood, he succeeded in obtaining from engines of that construc- 

 tion a very much better performance than had yet been effec- 

 ted by Mr Watt^^s engines. Mr Woolf and his friend, the late 

 Dr Alexander Tilloch, by their frequent publications on the 

 subject, industriously propagated the opinion of this superio- 

 rity ; and to this and Mr Woolf's alleged experiments are due 

 the very absurd notions of the great economy from the use of 

 highly elastic steam, which for so many years obscured that 

 quarter of the scientific horizon. We believe the explosion 

 of this theory (if it be worthy of the appellation) was effected 

 by Mr Dalton''s discovery of the law which determines the 

 dilatation of the permanently elastic fluids by increase of heat. 

 We are informed, that, soon after the erection of some of Mr 

 Woolf 's engines in Cornwall, one which worked at Huel 

 Abraham mine, during a trial which was continued for twenty- 

 four hours, lifted seventy millions of pounds one foot high by 

 the combustion of one bushel of coal. 



By dint of great attention to the joints, &c. of the engine 

 at Huel Abraham, its average duty was very far beyond that 

 of Watt's engines, then at work in the neighbourhood ; a 

 statement of their performance being periodically published. 

 The adventurers in mines and the engineers now began to 

 see the important advantages to be derived from attention to 

 proportion and accurate workmanship, and the founders in 

 Cornwall erected apparatus for the preparation of machinery 



