14 REPORT—1848. 
descending pump trees, the pistons were made to communicate with the 
main chain through a collar of leathers or stuffed collar, that then the whole 
of the machinery would stand together just above the level or sough, and 
there would take up less room, as the work might in general be comprehended 
within the limits of the shaft; and the descending pipe might also be of a less 
bore and be fixed in a corner of the shaft, and therefore be upon the whole 
much more convenient for underground works; and in this mode the latest 
engines of Mr. Westgarth were actually constructed with success. So that 
little was wanting, except the perfection of modern workmanship, to render 
the engine complete, although it was not made direct-acting, as the engines 
recently made generally are. 
Mr. Smeaton constructed a water-pressure engine in 1770 at Temple 
Newsam, Yorkshire, to work a pump for supplying Lord Irwin’s residence. 
It was of course of small size, and the pressure being communicated to the 
cylinder by an inclined pipe bringing the water from some distance, he modi- 
fied and improved the plan of Mr. Westgarth, closing the cylinder top and 
using the piston-rod with a stuffed collar, still however retaining in its original 
form, or nearly so, the ingenious slide valve devised by Mr. Westgarth. 
This was a cylindrical hoop or ring, sliding for a short distance up and 
_ down upon a pipe, which it encircled, the pipe having two sets of openings 
separated by a horizontal bridge or partition. The valve was inclosed in a 
box attached to the branch pipe of the cylinder, and sustained the pressure 
of the column equally in all directions; and it was rendered water-tight by 
strips of leather. 
When the upper openings in the pipe were exposed above the valve, the 
water entered the cylinder below the piston, but when the lower set of aper- 
tures was opened by raising the cylindrical valve, the water escaped from the 
cylinder, the position of the valve at the same time shutting off the further 
entrance of the water and its pressure upon the piston. The openings were 
in the first instance square holes, but afterwards they were made in the form 
of a lozenge or rhombus, with the acute angle upwards, so that the water 
might enter or be shut off more gradually. 
After Mr. Smeaton’s time the water-pressure engine seems to have re- 
mained in abeyance, and I am not aware that any more of them were made 
until Mr. Trevitheck revived their use. The great improvements made in 
the steam-engine by Mr. Watt caused water-engines of all kinds to be neg- 
lected ; and even water-wheels were in many cases replaced by steam-engines 
as their substitutes. Water power went out of fashion, and was generally 
considered to be too precarious and expensive, as compared with steam, to de- 
serve much attention from engineers. 
Lately, however, more enlarged views have been taken respecting water 
power, and the subject has been more studied and better understood. Instead 
of depending on the uncertain flow of streams and rivers, sometimes flooded 
and sometimes dried up, water has been stored in vast reservoirs, collecting 
the surplus rain from higher ground and ensuring a constant supply at all 
seasons, thus rendering water power both certain and cheap. The Bann 
reservoirs in Ireland and the Shaws water-works in Scotland may be taken as 
examples of this kind well-worthy of imitation. 
Mr. Trevitheck constructed several water-pressure engines, one of which 4 
was erected in Derbyshire in the year 1803, and is still, I believe, at work at 
the Alport mines, near Bakewell, to which it was removed from its original 
sitvation, not far distant. 
Through the kindness of Mr. John S. Enys of Penryn, I have been fa- 
youred with extracts of letters from Mr. Trevitheck to Mr. Davies Gilbert, 
