28 
THE CORNISH PUMPING ENGINE. 
The same request was also preferred by many of the proprietors of mining works 
in Cornwall, who foresaw that the use of the patented improvements would soon 
become essential to their interests, but at the same time dreaded the expenditure of 
money which would be entailed upon them by the necessity of pulling down the 
atmospheric engines and substituting the new ones in their place. 
The request was refused, and the alternative of the further outlay of capital was 
forced upon the adventurers. The motives which led Mr. Watt to this refusal are 
stated in his own answer to Smeaton’s application: the following is an extract from 
the letter, dated 1778. 
“ I have several times considered the propriety of the application of my condensers to 
common engines, and have made experiments with that view upon our engine at Soho, but 
have never found such results as would induce me to try it any where else; and in conse 
quence, we refused to make that application to Wheal Virgin mines in Cornwall, and to some 
others: our reasons were, that though it might have enabled them to have gone deeper with 
their present engines, yet, the savings of fuel would not have been great, in comparison to the 
complete machine. By adding condensers to engines that were not in good order, our engine 
would have been introduced into that county (which we look upon as our richest mine) in 
an unfavourable point of view, and without such profits as would have been satisfactory, 
either to us or to the adventurers; and if we had granted the use of condensers to one, we 
must have done so to all, and thereby have curtailed our profits, and perhaps injured our 
reputation. Besides, where a new engine is to be erected, and to be equally well executed in 
point of workmanship and materials, an engine of the same power cannot be constructed 
materially cheaper on the old plan than on ours; for our boiler and cylinder are much 
smaller, and the building, the lever, the chains, together with all the pump and pit-work, are 
only the same.” 
40. In 1782, Watt took out his third patent, for the expansion engine, by which 
he proposed to gain a considerable degree of power by the expansion of the steam 
in the cylinder, after its communication with the boiler had been closed. 
The important principle involved in this invention, which has since been worked 
to so great an extent and with such remarkable success, had been previously made 
known, as applied in a different form, in a patent taken out by Jonathan Horn- 
blower, of Penryn, Cornwall. 56 As some misrepresentations have been made, and 
56 Jonathan Hornblower was the son of an engineer, or rather a manufacturer of engines, of the same 
name, who is said to have been introduced into Cornwall by Newcomen, about 1738, and who was one of 
the principal makers of the atmospheric engine for that district. Young Jonathan was apprenticed to a 
plumber or pewterer, and for some time followed his trade (at that period one of considerable importance) 
at Penryn. He afterwards turned his attention to engineering, and became, in a little time, one of the 
principal engineers of the Cornish mines, which occupation he held till his death, about 1812 or 1813. 
He always maintained an excellent character in Cornwall, and was much esteemed by all who knew him