CATALOG OF THE MECHANICAL COLLEtmONS 1Q5 



gases to return through the flue, divide at the front, and pass back 

 along each side. 



From the wagon type of boiler the horizontal cylindrical shell 

 boiler soon developed, and following it came a great many combina- 

 tions of cylinders and drums in large and small sizes. The exter- 

 nally fired cylindrical boiler with convex ends and no flues was prob- 

 ably the most widely used boiler from 1800 to about 1850. Woolf's 

 patent steam-engine boiler, 1803 (see below), is an early and typical 

 one of combinations of small cylinders and drums, a modern example 

 of which is the "elephant", or French, boiler still used to some extent 

 in Europe. It is very probable that such combinations of drums and 

 connecting pipes suggested the water-tube boiler. 



The internal flue boiler was employed by Smeaton, the English 

 engineer who is often credited with its invention (c. 1740 to 1770), 

 as well as by Watt, as mentioned above. The real development 

 began, however, with the work of Oliver Evans in the United States 

 and Richard Trevithick in England. A model of a locomotive sup- 

 posed to have been made by Trevithick before 1800 has a horizontal 

 cylindrical shell boiler within which is a large circular flue passing 

 through the shell. Within one end of the flue a grate is provided, 

 and the other end of the flue is joined to a stack. Trevithick's pat- 

 ent of March 24, 1802, and a road locomotive constructed at London 

 in 1803 include a boiler of this type in which the flue was bent in 

 the form of a large U, and the hot gases were required to pass through 

 the entire length of the boiler in each direction. Trevithick con- 

 structed several large stationary flue boilers with great success. 



Oliver Evans, pioneer builder of high-pressure steam engines, is 

 generally credited with having made the first practical flue boilers 

 in the United States. Evans is believed to have completed his first 

 steam engine in 1802, but it is not clear what type of boiler he used 

 then. The Abortion of the Young Steam Engineers Guide^ by Oliver 

 Evans, printed at Philadelphia in 1805, illustrates a steam engine 

 (see above) "on the new principle" (high pressure), including a 

 section of an internally fired flue boiler. The text indicates that he 

 also used externally fired return-flue boilers and mentions his expe- 

 rience with boiling linseed oil in wooden boilers to 120 pounds per 

 square inch pressure and 600°. Evans also used the brick-set multi- 

 ple-drum boiler of several connected small cylinders all externally 

 fired, in the steamboat Aetna of 1818. 



Wooden boilers were used by engineers other than Evans, but they 

 seem to be a peculiarly American development. Just as the early 

 cookers of the various trades were used in England as steam genera- 

 tors, in the United States the wooden vats and tanks of the brewers 

 and distillers were to some extent adopted. Staudinger and Livings- 



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