96 IMPROVEMENTS IN STEAM ENGINES. 



which passes through the boiler. H, the flue round the outside 

 or" the boiler, wherein the fire is carried until it enters the 

 chimney at I, Fig. 5. The whole boiler is tied together inter- 

 nally by numerous braces, Fig. 10, which are forked and bol- 

 ted together upon the flanches, and are indispensable to pre- 

 vent the boiler from bursting. The flanches and joints of the 

 castings are represented Fig. 6, 7. 



The boiler is composed of 70 plates of iron, cast with 

 flanches, and bolted together, so that the flanch and bolts are 

 within the water of the boiler wherever the flame touches it; 

 otherwise they would be burned off in a few days. The pieces 

 are so contrived as to be of only 12 different patterns. This 

 boiler consumed 50 bushels of coal, and 4 a cord of wood, 

 while rolling iron 12 hours, at 20 strokes per minute, and 

 pumping water 6 hours, at 12 strokes per minute. 



I will only further observe, that this boiler requires a very 

 active fire-man; and it is my opinion, that if it were 3 feet 

 longer, a more moderate fire would raise the same steam and 

 consume less fuel. The permanence of this boiler renders it 

 very superior to the wooden one; and the difference of the 

 consumption of fuel in each, in proportion to the size of the 

 engine, is not great. 



The further improvement of the engine itself consists in a 

 new application of an improved construction of the air-pump. 

 I will first remark, that by the air-pump of Bolton and Watt, 

 the condenser is only once emptied, of its water of conden- 

 sation and of the air produced, in every stroke. The supe- 

 riority of our air-pump consists in its evacuating the conden- 

 ser twice at every stroke, thereby creating a much better 

 vacuum, and of course adding considerably to the power of 

 our engine in proportion to the diameter of its cylinder with- 

 out encreasing friction. The drawing, Plate II, Fig. 8, will 

 best explain the construction of this pump. 



A, is the pump-barrel. B, the piston which is solid. C, the 

 condenser. D, a pipe of connection between the condenser 

 and the lower chamber of the air-pump. E, a pipe of con- 

 nection with the upper chamber of the air-pump. F, valves 

 opening towards the air-pump. G, discharging-valves into 



