408 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



course, underneath ; so that the tubular boiler may also be considered 

 as one with an inside fire. It certainly has all the advantages of one. 

 Fig. 283 gives an example of a marine tubular boiler, which is 

 at the same time a boiler with return flame, since the gas from 

 the fire before playing upon the tube passes first through two large 



FIG. 285. Arrangement of tubes 



FIG. 284 Sectional elevation of Shand and Mason's 

 inclined water tube boiler for fire-engines. 



FIG. 286. Horizontal section. 



cylinders, A and B, runs back at the end of the boiler, and returns 

 again by the tubular pipes to the chimney where it escapes. 



We have in the case of the fire-engine an illustration of the 

 manner in which such a construction of boiler is utilized when it is 

 necessary to get up steam rapidly, Fig. 284 represents a sectional 

 elevation of Shand and Mason's inclined water-tube boiler and in 

 steam fire engines. A is the furnace ; B the heat-absorption chamber 

 (sectioned on the line I, J, Fig. 286) ; c the chimney or funnel ; 



