346 TUBULAR BOILER, SUPERHEATING STEAM, 



made through the sides of all the four tubes of the condenser 

 and air-vessel opposite to and as wide as the fire-place opening 

 through the sides of the boiler. The upper part of both 

 openings to be of the same height, but the outer opening is 

 made as low as the bottom of the boiler, in order to allow room 

 for a pipe to enter that part of the boiler for forcing the water 

 into it, and also another pipe and cock for drawing off the water 

 or sediment, in case foul water be used by accident or careless- 

 ness. These two openings through the condenser and air-vessel, 

 and through the boiler, constitute one fire doorway through all 

 the six tubes for access to the fire-place ; a ring is placed 

 between the two tubes of the condenser around the fire door- 

 - way, so as to cut off all communication of the steam in the 

 condenser with the air in the doorway ; another similar ring is 

 placed between the condenser and the outer tube to prevent 

 the escape of air into the fire doorway, and a half ring is placed 

 in the lower part of the fire doorway between the condenser 

 and the inner tube of the air-vessel, to prevent ashes from 

 falling into the air-vessel, and yet allow a free passage for the 

 air from the inner part of the air-vessel into the upper part of 

 the fire doorway. These two rings and the half ring are 

 secured in their places by rivets passing through all of them 

 and through the tubes, and uniting all firmly together, the 

 interstices being filled with iron cement. A ring is also placed 

 between the boiler and the air-vessel around the fire doorway, 

 against the outside of which ring the charcoal powder is tightly 

 rammed, and will hold the ring in its place without the neces- 

 sity of either rivets or screws. That part of the fire doorway 

 which is above the fire-bars is supplied with an inner door, to 

 shut the fire-place even with the outside of the boiler, and 

 exclude all access of air to the fire, except through the grating. 

 The whole of the fire doorway is enclosed by an outer door even 

 with the outside of the air-vessel, to exclude all air, except that 

 which comes through the air-vessel; a pipe is fixed in the 

 bottom or dish-piece leading to a forcing pump to draw the 

 water out of the condenser and force it into the bottom of the 

 boiler through the pipe before described. A blowing cylinder 

 of about ten times the content of the main cylinder is screwed 



