348 TUBULAR BOILEli, SUPERHEATING STEAM, 



supplying vessel, which sediment or salt may be occasionally 

 blown out through the bottom pipe by filling the vessel with 

 water, shutting the water, steam, and air cocks, and opening 

 the cock of the outlet pipe at a time when the steam in the 

 vessel is strong. But the supply of water from the condenser 

 being always equal to that converted into steam and used in 

 the engine, there is no tendency to a variation in the height of 

 the water in the boiler, except there be leakage or waste of 

 steam in some part of the engine. An upright glass tube, 

 having an iron tube of communication with the lower part of 

 the boiler and another iron tube of communication to the upper 

 part of the boiler, is conveniently placed against the outside of 

 the air-vessel to indicate at all times the height of the water in 

 the boiler ; as is usual in steam-boilers, a valve is placed on the 

 top of the air-vessel to allow of the escape of a portion of the 

 air in case that the quality of the fuel should not require 

 so much air for perfect combustion as the steam requires for 

 good condensation. The degree of the condensation of the 

 steam may be increased at pleasure, by increasing the velocity 

 of the air passing into and through the air-vessel. The other 

 parts of my improved steam-engine, such as the steam-pipes, 

 the throttle-valve, the saf3ty-valve, the vacuum-valve, the 

 working valves, crank, connecting rods, cross-heads, pistons, 

 piston-rods, and various other minor parts common to engines 

 in general use may be made in the usual forms, and placed in 

 the most convenient situations ; they cannot, therefore, need 

 any description. When it is intended to use water for con- 

 densing instead of air, my improved steam-engine must be made 

 as before directed, except that the communication between the 

 air-vessel and the fire-place must be closed, which may be done 

 by a perfect ring of iron surrounding the opening leading to the 

 lire-place, instead of the half ring before described, and a forcing 

 pump must be employed to draw water from a reservoir, and 

 force it into the vessel which I have hereinbefore denominated 

 the air-vessel, but which in this mode of working would more 

 properly bear the name of water-vessel. In this case a blowing 

 cylinder, the dimensions of which must be calculated according 

 to the quality of the fuel to be used, may be worked to blow the 



