176 Description of Mr Perkins’s New Steam-Engine . 
cold water is introduced from the reservoir Z, by means of the 
pipe 7, 7, 7, loaded with five atmospheres. 
From the high elasticity of the steam employed in this engine, 
it has been supposed to be very liable to explosion. This, how- 
ever, is a vulgar error. Since there is no reservoir of steam ex- 
posing a large surface to its expansive force, as in the common 
high pressure engines, the steam being generated only in suffi- 
cient quantity to produce each succeeding stroke of the piston, 
the ordinary source of danger is entirely removed. But, in or- 
der to take away all apprehensions on that subject, the induction 
pipe 2, 2, 2, in which the steam is actually generated, is made 
so strong as to sustain an internal force of four thousand pounds 
on the square inch, which is eight times more powerful than the 
actual pressure, viz. 500 pounds on the square inch, with which 
the engine works. This enormous superabundance of strength is 
still farther secured by means of the safety -pipe 8, 8, 8, provided 
with a thin copper “ safety-bulb” a b , which is made so as to burst 
at a pressure of 1000 pounds on the square inch. In order to sa- 
tisfy his friends on this very important point, Mr Perkins has re- 
peatedly urged the power of the steam to such a degree as to 
burst the copper bulb in their presence. This tube merely rends, 
or is torn asunder like a piece of paper, and occasions no injury 
either to the spectators, or to the apparatus ; so that we have no 
hesitation in considering this engine, notwithstanding its tremen- 
dous energies, much more safe in its operations than even the 
common low pressure engine. 
The safety tube 8, 8, 8, communicates also with the indicator 
c d, having a dial-plate ce y and an index e f which, by means of 
a suitable contrivance at v, v , indicates the pressure or number of 
atmospheres with which the engine is working. 
The cylinder and piston PPQ, have been separated from the 
rest of the engine, for the sake of distinctness. Their proper 
position, however, will be understood by supposing the two lines 
9,9 ; 9 9 to coincide. 
The engine which we have now described, is at present per- 
forming actual work in Mr Perkins’s manufactory. It is calcu- 
lated as equal to a ten-horse power, though the cylinder is no more 
than 2 inches in diameter, and 18 inches long, with a stroke of 
only 12 inches. Although the space occupied by the engine is not 
