THE CORNISH PUMPING ENGINE. 
23 
the boilers were free from the danger of leakage from this cause. This alteration, 
combined with the careful management of the firing Watt insisted on, contributed 
much to the economy of the engine. 
34. The manufacture and workmanship of the engine generally was also much 
improved by the ingenuity and perseverance of Watt and his assistants. Indeed, a 
new school of engineering manufacture may be said to have been formed at Soho : 
the workmanship of the engines or parts of engines made there, was excellent, and 
the patentees were careful that all work done for their engines elsewhere should be 
carefully executed, lest their interests might suffer from the unnecessary waste that 
might result from the working of an engine badly made. 
35. Watt’s engines in Cornwall were erected at the expense of the parties using 
them, and frequently were constructed by the engineers in the neighbourhood, (with 
the exception of particular parts, such as the valves, &c., usually made at Soho;) 
Messrs. Boulton and Watt furnishing such drawings and directions 44 as were neces 
sary for their manufacture and fixing. For this and for the patent right, it was 
agreed that the patentees should be remunerated, not by any fixed sum, but by a 
payment equivalent to the value of one-third of the fuel saved by the improve 
ments. 
It was offered to accept a composition of ten years’ value of the savings, in lieu of 
annual rent; but in Cornwall, where the mines themselves were generally considered 
worth only three or four years’ purchase, this arrangement was not favorably re 
ceived. 
When Boulton and Watt were first introducing their engines into Cornwall, being 
anxious to afford the miners every facility in order to meet the objections raised 
against the outlay of capital required for the purchase of the patent engines, they 
frequently took the old atmospheric engines in part payment of the price of the new 
ones, and also gave credit for the remainder of the purchase money. In some 
instances they even erected the engines at their own expense, considering them 
their property, and repaying themselves by the profits accruing from their working. 
These allowances were, however, discontinued as the engine became in greater re 
quest, and its merits more generally known. 
44 Messrs. Boulton and Watt issued a printed book of ‘ Directions for erecting and working the newly 
invented Steam Engines,’ which contained very explicit instructions for fixing the engines and keeping 
them in order ; illustrated by plates of the details. Copies of this book are now extremely scarce ; I have 
been favored by Mr. George Rennie with the loan of one, which was the property of the late Mr. John 
Rennie, formerly one of Mr. Watt’s ablest coadjutors. From this copy I have quoted in the following 
pages. The work is without a date, but was evidently written for the early engines.