346 EXPLANATION OF THE PLATES. 



PLATE XVII. 



Fig. 1 . is a section of a steam vessel with its boiler in two parts ; the right part 

 is shown in a section across it through one fire-place F, and its flues N, P ; and 

 through the cross flue L of the other fire-place, and through the safety valve U 

 (art. 263.) ; showing the dampers O, R, and the passages of the flues to the 

 chimney. Of the left part the fire-door end is shown with the fire-doors D D, the 

 handles for clearing the clinkers B B, the doors for cleaning the flues at E E E, 

 and the gauge cocks G ; also part of the chimney C, the steam pipe S, and a slide 

 valve V, to shut off" the steam from the engine. There should be as much space 

 between the boiler and the sides of the vessel, as to admit a person to go round to 

 examine it. The floor under the boiler should be rendered as strong as possible, 

 and the boiler should rest on a plate of iron bedded on a layer of bricks or tiles 

 laid over the floor in cement ; in this manner a thin plate of wrought iron ex- 

 tending under the whole, being flexible, and brick a slow conductor of heat, is 

 more secure than a much thicker cast-iron plate. 



Fig. 2. is a plan, showing the arrangement of the two fire-places F F, and their 

 flues. The fire-door is at D, the fire on the grate F, the clinkers fall at H, and 

 the smoke turns at L and returns along the flue N, rises at O, and goes back along 

 a flue P over N. The boilers should be strengthened by internal frames disposed 

 in triangles, and so as to afford supports for the flues. 



Fig. 3. is a longitudinal section through the boiler, and one of the fire-places : l the 

 same letters refer to the same parts in all the figures ; see art. 239 244. : for the 

 fire and flue surface, art. 204. : for the capacity, art. 215 220.; for the area of 

 the chimney, art. 278. ; for safety valves, art. 259 272. ; for the strength of 

 boilers, art. 525. ; and for the management of sea water, art. 565. 



1 In this last figure there is scarcely sufficient space allowed for the action of the slide valve V. 



