IMPROVEMENTS IN STEAM ENGINES. 95 



CAST-IRON BOILER. 



Within the last few months, a cast-iron boiler has been put 

 up, at the lower engine, which hitherto exceeds the expec- 

 tion, I had formed of the facility with which steam is raised 

 and supported by it. The engine is a double steam-engine, of 

 40 inches cylinder, and 6 feet stroke. The boiler has straight 

 sides, and semicircular ends; it is 17 feet long, and 8 feet wide 

 at the bottom; and nineteen feet long, and 10 feet wide at 

 the height of 5 feet 7 inches. At this height, it is covered 

 by a vault; which, in its transverse section, is semicircular; and 

 in its longitudinal section exhibits half of its plan. The bot- 

 tom is concave every way; rising one foot in the center. The 

 fire-place is 6 feet long, and at an average 4 feet wide; and 

 is under one extreme end of the bottom. The fire-bed is 

 arched, parallel with the bottom, leaving a space of one foot 

 high, for the passage of the flame. At the end opposite to 

 the lire-place, the flame descends along the bottom of the 

 boiler, and, passing under an arch of fire-bricks, which pro- 

 tects the flanch of the bottom, strikes the side of the boiler at 

 its extreme end. Here it enters a flat elliptical flue, which,, 

 passing into the boiler, follows its form, returning again and. 

 coming out near the place at which it entered. The entering 

 part of the flue is separated from the returning flue, by a par- 

 tition of fire-bricks. The flue, on coming out of the boiler, 

 turns short round, and is carried round the whole boiler until 

 it enters the chimney; as will be more clearly shewn by refer- 

 ring to Plate II. Fig. 5,6, 7; the same letters on each figure refer- 

 ring to the same things. Fig. 5. C, a horizontal section of the 

 boiler, through the center of the flues. Fig. 6. B, a transverse 

 section of boiler at the lire-grate. Fig. 7. A, a longitudinal sec- 

 tion. Fig. 6,1. D, the fire-bed. K, a bridge- wall nineinches thick, 

 over which the fire passes to the passage E, under the bottom 

 of the boiler, being parallel both ways with the same. Fig. 7. 

 L an arch of fire-bricks to support and protect the flanch from 

 being melted by the heat. Fig. 6, 7. The fire passes from D, 

 through the passage E, under the arch L, Fig. 7, to the take- 

 up E, Fig. 5, 7, where it enters the upper flue G, Fig. 5, 6, 1, 



