328 EXPLANATION OF THE PLATES. 



PLATE I. 



Fig. 1. is an isometrical projection of a rectangular steam boiler, (art. 225, 226.) 

 with part of the top plates of the boiler, and part of the brickwork removed to show 

 the internal parts. A is the boiler ; the half of the doorway to the fire is at B, and 

 the fuel rests on the fire-bars G, and against the back F : the flame passes over F, 

 and along under the bottom ; it rises at H, and returns in a flue by the nearest 

 side, passes round the end by the flue I, and along a flue by the further side to the 

 chimney at L; a horizontal damper K regulates the aperture to the chimney. 

 See art. 257. The door to the ash-pit C should shut perfectly close, and the 

 supply of air for the fire should enter by a passage E, the aperture of which is 

 regulated by the force of the steam acting by the chain n, n, (art. 258.) In the 

 figure the air is supposed to enter by the grating at D. The supply of water enters 

 by the pipe M N, the end N being turned along the bottom of the boiler, that the 

 water may acquire heat before it mixes with the rest ; the admission is regulated 

 by the stone float c. (art. 251 253.) The steam passes to the engine by the pipe 

 S, and when it is not required, it goes off by the safety valve V, (art. 260.) and 

 through the pipes T W. The internal valve is on the man-hole plate at a b, 

 (art. 259.) The steam gauge is at h, (art. 558.) the gauge cocks at k, i ; and a 

 cock to clear the boiler of water is at R. Opposite each flue, as at Q, there must 

 be an aperture to clear it out at. 



Fig. 2. shows a method of admitting water to a boiler where high pressure steam 

 is used. The pump forces the water by the pipe D, through the valve aperture A, 

 into the boiler ; but when the quantity is in excess, the copper float F closes the 

 valve, and opens the valve B to the waste pipe C, by which the surplus passes off. 

 The parts must be balanced on the axis by the weight G. (See art. 253.) 



Fig. 3. 4. 5. and 6. are tops for engine chimneys. Fig. 3. is a plain obelisk : the 

 proportions of an Egyptian obelisk are very well adapted for a chimney, and if the 

 faces were stuccoed and covered with sunk figures, it would render them novel and 

 ornamental. Fig. 4. is an octagon top for a square shaft ; Fig. 5. an octagon 

 chimney ; and Fig. 6. a chimney to represent a column. (See art. 274 278.) 



