Steam-Engines in Cornwall. 37 



The performance of the steam-engines gradually increased to 

 an average of between twenty and twenty-five millions, the lat- 

 ter being by no means a frequent occurrence. 



Mr Sims now erected two or three engines on a plan which 

 was a combination of the high pressure with Watt's, and their 

 average was probably little short of thirty millions ; however, 

 this advantage was entirely attributable to the greater degree 

 of attention paid to their erection. 



During or about the year 1820, the well-known and exten- h 

 sive consolidated mines in Cornwall were put into active ope- 

 ration, and Mr Woolf, who was appointed the engineer, ex- 

 pressed an intention to erect some engines of the two cylinder 

 construction. This was opposed by Mr William Francis, a very 

 intelligent mine-agent in the employ of Mr John Taylor, and 

 in consequence, some very large engines on Watfs principle 

 were made. Every attention was paid to proportion and work- 

 manship, and their performance fully justified Mr Francis's 

 views of the subject. 



The unprecedented activity of mining enterprize which 

 immediately succeeded required the preparation of many new 

 and powerful steam-engines, and in their construction as much 

 attention was given to the proportion and preparation of the 

 parts as the scientific attainments of the superintendents af- 

 forded. Forty and even forty-eight millions was not now 

 considered a singular occurrence. Much of the credit of 

 this is unquestionably due to Mr Woolf. The superiori- 

 ty of Mr Watt's engines was now considered beyond doubt ; 

 and but one of Mr Woolf's has been since erected. Towards 

 the termination of the year 1826, Mr Grose was called on to 

 superintend the preparation of some steam-engines at Huel 

 Towan mine ; and the average duty of that which was first 

 worked was nearly fifty millions. A coating of saw dust of 

 about ten inches in thickness was now applied to the steam- 

 pipes, nossel, cylinder, &c. and about an equal depth of ashes 

 to the top of the boiler. The duty was by this means increas- 

 ed to about sixty-five millions. A loss of caloric still obtaining, 

 another coating of about the same depth, and of like materials, 

 was applied outside the former, the consequence of which 

 was a further increase to eighty-seven millions, which was the 

 average of a trial at which the writer of this notice was pre- 



