THE CORNISH PUMPING ENGINE. 
29 
as probably erroneous ideas exist, as to the nature of the respective claims of Watt 
and Hornblower to the merit of the invention, a brief statement of the principal 
facts connected with it may not be irrelevant in this place, particularly as this 
subject, of all others, most nearly concerns the Cornish engine as distinguished 
from other varieties. 
It appears that Mr. Watt, as early as 1769, gave, in a letter to his friend 
Dr. Small, of Birmingham, a clear and explicit description of the general principle, 57 
but it was not put into practice by him with any view to economy from its use 58 
before 1776, when an engine at Soho Works was altered to work expansively. In 
1778, another engine at Shadwell was experimented upon, and Watt took out his 
patent March 12th, 1782, immediately after which date the invention was put in 
practice in Cornwall and elsewhere. 
or employed him. In the unfortunate disputes with Boulton and Watt, which were carried on ostensibly 
by him, he is represented to have been more sinned against than sinning, and to have been thrust forward 
by parties whose interest it was to keep in the back ground themselves while their battles were being 
fought by others. He was of a very ingenious turn of mind, which was combined with sound practical 
knowledge and judgment. His engines were always well made, and bore a good character at a time when 
almost all others in the county had become much deteriorated. His invention of the double-cylinder 
engine would alone, if he had done nothing else, cause his name to be remembered as long as the steam 
engine exists, or its history remains upon record. 
It is, however, singular that the mistaken and over-driven zeal of some of Watt’s friends has led them 
to think it necessary to Watt’s fame, that the merits of Hornblower should, if possible, be buried in 
oblivion. For not only have the most unfounded calumnies been circulated to his disadvantage, but his 
inventions have industriously been ascribed to other parties; his name and the accounts of his works have 
purposely been concealed; and those who have attempted to take his part have been persecuted for their 
liberality. We may however hope, for the credit of our country, that this morbid feeling is now gone by, 
and that, while we yield to none in the high and deserved honour we ascribe to the great and immortal 
improver of the steam engine, yet we may be permitted to give the due share of merit to others who have 
laboured industriously and not unsuccessfully in the same field. 
Jabez Carter Hornblower, Jonathan’s brother, was well known as an engineer of celebrity, but was 
principally engaged out of Cornwall. A sketch of his life may be found in * Stuart’s Anecdotes of Steam 
Engines,’ page 638. The brothers have often been mistaken for each other. 
67 Farey on the Steam Engine, page 339. 
58 Watt anticipated the principle of expansion, in some measure, in his earlier engines, where the steam 
was generally cut off somewhat before the termination of the stroke of the piston; but this was done in 
order to regulate the motion, and to bring the moving mass quietly to rest by the expansion of the steam, 
and not ostensibly with any reference to gain of power. It was also intended by Watt as a means of 
adapting the power of the engine to the load upon it, and so it remains to the present day: in the 
‘ Book of Directions ’ already alluded to occurs this passage (Art. liii. page 17) : “ This regulation may be 
effected in two ways, either by opening the top regulator fully at the beginning of the stroke, and shutting it 
before the piston arrives at the bottom, or by opening it so far as just to give the piston a sufficient velocity, 
and keeping it open until the end of the stroke.” This was written before the date of Watt’s expansion 
patent, but long after the intimation of his idea to Dr. Small; so that it is very probable Watt had a view 
to economy by expansion in his mind, but did not think proper at that time to make it public.