366 



On the Construction of Kitchen 



and part of the side of a boiler; E is a section of a 

 descending rim of wood belonging to and making an 

 essential part of the cover, which rim, when the cover 

 is down, enters the steam-rim of the boiler, and reposes 

 on the bottom of it. In the figure it is represented in 

 this situation : the wooden rim of the cover is fastened 



to the flat part of it by means of wood-screws, one of 

 which is represented in the figure.* 



Now it is evident, from an inspection of the figure, 

 that a small quantity of water will lodge in the steam- 

 rim, and will stand at the level of the dotted line, F, G ; 

 and, as the rim of the cover will enter this water when 

 the cover is shut down, all communication between the 

 steam in the boiler and the external air must necessarily 

 be cut off, and of course the steam will be completely 

 confined. 



It is true that, if in consequence of the increase 

 of its temperature above the heat of water boiling in 

 the open air the elasticity of the steam should become 

 sufficient to overcome the pressure of the atmosphere, 



* The cover itself is supposed to be framed and panelled in the manner 

 described in the fifth chapter of this Essay, and it should be lined with tin or 

 with thin sheet copper tinned, in order to prevent the wood from being cracked 

 and destroyed by the steam. 



