THE WATT AND THE TREVITHICK KXCJIXES. 127 



This high-pressure puffer pumping engine at Green- 

 wich, in 1803, worked a pump of 18 inches in dkmeter. 

 The engine boy having fixed the safety-valve while he 

 fished for eels, caused an explosion of the boiler. This 

 was the first mishap from the use of high-pressure 

 steam. The boiler was globular, 6 feet in diameter, and 

 from an inch to an inch and half in thickness, made of 

 cast iron ; the cylinder, of 8 Inches in diameter, was 

 partly let into and fixed on the boiler. Its general 

 design is seen in the patent drawing of 1802, Fig. I. 1 

 Trevithick determined in future to use two safety-valves, 

 and also a safety steam-gauge. At that time one of his 

 high-pressure puffer-engines, with a cylindrical boiler 

 and internal tube, was working in Staffordshire. 



The G-reenwich high-pressure puffer-engine did four- 

 teen millions of duty with a bushel of coals, 84 Ibs. A 

 60-horse-power engine was being built in Wales, with 

 an 8-feet stroke, to work expansively with 30 Ibs. of 

 steam on the inch in the boiler. For a more thorough 

 test with the low-pressure vacuum engines, in com- 

 petition, the Government intended to use the new 

 engines, and some of Watt's engines having been re- 

 moved to make room for them, Boulton and Watt wrote 

 to a gentleman who was about to order an engine from 

 Trevithick, " We knew the effects of strong steam long 

 since, and should have erected them, but knew the risk 

 was too great." Moreover, " it was an invention of 

 Mr. Watt's, and the patent (Trevithick 's) was not worth 

 anything." This admission clearly shows not only that 

 Watt did not make high-pressure steam-engines, but 

 that he did his best to prevent others from making 

 them. 



1 Sec vol. i., p. 128. 



