i.9B 
Steam Engine, 
possible quantity of coals, as it combines the advantages 
of every other engine hitherto known. By detaching the 
air-pump and condenser (which may be done in half an 
hour) atid where water cannot be had for condensation, 
this engine may be worked by the pressure of strong steam 
alone, as the internal cylinder is kept as hot as the steam 
in the boiler.^ This dangerous plan never ought to be 
resorted to but in cases of necessity, as it is no saving of 
coals, and as there can be no certain rule when to dis» 
continue the use of the boiler, the weakness of which is 
not prevented by putting the fire in a tube in the inside of 
it. This engine requires no framing nor miil-wright 
^voYk in the fixing, but merely bolting down to the Boor 
it stands upon. It takes up very little room, and all its 
parts are within reach, without the necessity of upper floors 
or stages, which would be the case if the beam was above ; 
but by being fixed below and alone, it has no tendency 
to move from its situation. 
Desanption of a portable Steam-engine^ invented by 
Mr. Samuel Clegg, David Street^ Manchester. 
Communicated by Mr. Dalton, Lecturer at the^ 
Royal Institution^ 
THIS engine is vrorked by four copper valves in the 
usual manner, but the mechanism for lifting them is very 
different from any hitherto made ; there are no levers em- 
* Many engines are at present worked in London and else- 
where by the mere force of steam, without condensation, under 
Trevethick’s patent. The force is from 45 to 60 lbs. on the round 
inch; a pressure equal to about 25 fathoms of water at the most. 
V arious assertions and reports concerning the safety, the economy, 
and the other effects of these engines have passed under my no- 
tice ; but the interested situation of some of the narrators on both 
sides, and the short time of trial, have induced me to wait for more 
facts before 1 should give any account of the engine in this Journal., 
X hope to do this a fe\y months hence.— W. N. 
