14 BULLETIN 119, U. S. NATIONAL MUSEUM. 



There existed at that time a great sphere for the employment of 

 such an engine in the drainage of the mines of Cornwall and Devon- 

 shire, for, although the miners made use of both animal and water 

 power to clear the workings from the steadily increasing flow of 

 water, the deepening of the mines increased the difficulties of remov- 

 ing the water by these means, and the limit of their use had about 

 been reached. Savery's engines were erected at several mines, but 

 only at those whose depth did not exceed the maximum lifting 

 capacity of the engine — about 80 feet. For deeper mines Savery 

 proposed the erection of as many engines as the increased depth of 

 the mine required; that is, a mine 250 feet deep would have three 

 engines, one 80 feet from the bottom, another 80 feet above the first, 

 raising water from a sump into which the first exhausted, and a 

 third engine on the surface to raise the water the remaining distance. 

 This maximum lift required a steam pressure of 30 pounds, and the 

 fuel consumption of the engine was very high, so that the combina- 

 tion of the necessity for the use of several engines, of the danger of 

 high boiler pressures, and of the low fuel efficiency greatly restricted 

 the use of Savery's engine. 



It is probable that this failure prompted Thomas Newcomen to 

 turn his attention to the subject, and about 1Y05 he perfected an 

 engine of the atmospheric type, which was without any of the features 

 objected to in the Savery, and from which the modern steam engine 

 can be directly traced. Newcomen's engine differed primarily from 

 Savery's in that it raised water by atmospheric pressure alone, the 

 steam being only used to create a vacuum. 



Although Newcomen included all of the valuable features of the 

 engines of his predecessors in those he built, the finished engine 

 was so superior to any that had gone before that it was practically 

 a new invention. It included the separate vessel in which to gen- 

 erate the steam ; likewise, through an accident which punctured the 

 cylinder, cold water was injected into the cylinder in order to effect 

 a speedy vacuum under the piston; and a valve gear was provided 

 whereby the machine could be made to repeat its movements auto- 

 matically. Since Savery's patent was sufficiently general to cover 

 Newcomen's engine, although the principal was different, the two 

 joined hands in the construction of engines, and for upward of 60 

 years after the introduction of the first engine Newcomen engines 

 proved to be the only economical agent for draining mines. 



During the years 1763-1764 James Watt, while engaged in repair- 

 ing a model of a Newcomen engine, was impressed by the enor- 

 mous consumption of steam and made some experiments and meas- 

 urements of the temperature, pressure, and volume of the steam 

 generated in the model, and also of the quantity of water required 

 to condense the steam. These experiments showed that the chief 



