CONSTRUCTION OF RETORTS. 67 



The distance between the centre and centre of these girders is six feet 

 nine inches. 



L is the furnace for heating the retorts : its breadth is 14 inches, the length 

 of the fire-bars 24 inches : they are represented in Fig. 14. 



Fig. 14. 



The bars are placed loosely upon the bearers, and must occasionally be 

 " clinkered," or lifted from their seat in the front and cleared from the slag 

 which adheres to them. 



MM... are side openings, three inches square, left in the brickwork, 

 through which the heat of the furnace passes. 



N N . . . are 4^-inch walls, built of Newcastle fire-bricks, one between each 

 of the openings M ; they serve to support the fire-tiles T, on which the out- 

 side lower retorts rest. The direction of the flues is shown by arrows. 



P P are fire-bricks, placed on end, and a fire-lump, upon which the two 

 upper retorts rest. The heat acting on these being somewhat moderated, no 

 guards of fire-tiles are necessary. 



O O are openings, 3 inches by 4^, in the crown of the main arch commu- 

 nicating with the branch flue. 



Q is the branch flue, one being built over the centre of each bench of 

 retorts. 



R is the main flue, running the entire length of the benches, and connected 

 with the chimney into which all the branches lead. Between this main flue 

 and each branch is a damper, Z, to regulate the draught through the fur- 

 naces. 



S'S'. . . are cast-iron plugs, covering sight-holes, through which the heat of 

 the retorts is seen and judged of. 



V is the furnace-door, protected by a fire-lump inside, as shown in Fig. 15. 



K 2 



