By Mr. Alexander Stewart 227 



back wall, it is the uppermost of those marked, 

 d, d, d; the other furnace supplies the two other 

 back flues, the smoke from it passes first along the 

 lower and returns by the middle flue. The space 

 marked e, is the recess behind the stages. A 

 ventilator marked/, opens by a slide two feet long 

 by one wide ; one of these is placed between each 

 stage. 



