B AHUS.] 
DEGREE OF CONSTANT TEMPERATURE. 
65 
graphite crucible F F, which was 14 inches high, 11 inches in largest 
diameter, and § inch thick. The graphite cover MM was luted on with- 
a paste of powdered graphite and water. Through the cover M M the 
iron tube L passed, extending downward into the crucible and closed 
at its lower end. An iron pipe, G, 1J inches in diameter, passed up 
through the bottom of the crucible about 6 inches, carrying the fire- 
clay spherical shell K K, and protected by a coating of lire-clay, I L 
Fig. 5. Boiling-point furnace for zinc; later form; longitudinal section. Scale, ^. 
Underneath the crucible a inece of stone-ware pipe, 6 inches in diam- 
eter, N N, was built into the furnace concentric with the crucible and 
extending 15 inches below it. In practice this pipe N N dips just below 
the surface of the water in a tank placed between the two fire-boxes 
A A. and not shown in the drawing. 
Bull. 54 5 (719) 
