Description of Mr, Perkins^ Mew Sieam-Engine, 115 



water now escapes through a valve opening outwards, along 

 4, 4, 4; thus effectually cutting off all direct or uninterrupt- 

 ed communication between the generator and the condens- 

 er. In order to keep the water in the condenser at a press- 

 are of 5 atmospheres, the blast of the bellows H goes round 

 the condenser STXV ; but when it is not sufficient for this 

 purpose, cold water is introduced from the reservoir Z, by 

 means of the pipe 7, 7, 7, loaded with 5 atmospheres. 



From the high elasticity of the steam employed in this 

 engine, it has been supposed to be very liable to explosion. 

 This, however, is a vulgar error. Since there is no reservoir of 

 steam exposing alargesurface to its expansive force, as in the 

 Common high presure engines, the steam being generated on- 

 ly in sufficient quantity to produce each succeding stroke of 

 the piston, the ordinary source of danger is entirely remo- 

 ved. But in order to take away all apprehensions on that 

 subject, the induction pipe 2, 2, 2, in which the steam is ac- 

 tually 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 satisfy his friends on this very important point, Mr. Perkins 

 has repeatedly urged the power of the steam to such a de- 

 gree as to burst the copper bulb in their presence. This 

 tube merely rends, or is torn assunder like a piece of papef, 

 and occasions no injury either to the spectators, or to the 

 apparatus ; so that we have no hesitation in considering this 

 engine, notwithstanding its tremendous energies, much 

 more safe in its operations than even the common low pres- 

 sure engine. 



The safety tube 8, 8, 8, communicates also with the indi- 

 cator c d, having a dial-plate c e, 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. 



