GEOLOGICAL SOCIETY OF PENNSYLVANIA, 



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1 . Cylindric boilers of considerable length. A large 

 tube passing concentrically through them. Fire applied 

 in the tube, and the heated air made afterwards to cir- 

 culate first under, and then along the sides of the boiler. 

 The area of the side flues are generally as large as the 

 area of the tube, and the passage is contracted by a 

 damper being placed in the tunnel, from the boiler to 

 the stack^ or chimney. 



2. In the management of the fire itself. The fire is 

 large and thick; the fire-bars open nearly to the full 

 breadth of the tube ; the coals are spread or dusted over 

 the surface of the fire ; the fire is never stirred or slaked, 

 except at the time of cleansing. The fireman, in cleans- 

 ing, first shuts down his damper to prevent the rush of 

 cold air, which would otherwise lower the steam in the 

 boiler, and turns the good fuel on one side, and raking 

 off the clinkers, (the only refuse) turns the fuel back on 

 the clean bars, and performs the same operation with the 

 other side. The fire, before cleansing, is about 6| 

 inches deep; and after cleansing, about 3 to 3|. By 

 closing the dampers, no decrease of steam is observable 

 during or after the operation of cleansing. The coal 

 which is preferred, is a mixture of various Welsh coals, 

 which clinker most in a brisker fire. 



3. In using steam of 20 to 50 pounds to the inch, and 

 in expanding the steam, by cutting off the communica- 

 tion between the boiler and cylinder, at one-fourth of 

 one-fifth of the stroke. 



4. In covering or clothing the boiler, steam pipes, 

 steam chests and cylinder, with a non-conducting sub- 

 stance, such as saw- dust or straw, where the heat of 

 steam only can be in contact; and " cobj" that is, clay 

 and straw, over the brick work of the fire. 



5. In suspending the action of the piston, at the 

 completion of its stroke, allowing time for the perfect 



