STATE GEOLOGIST. 243 
supported by two bricks, petroleum being fed into this pan by means of a 
4 inch pipe. The oil was forced in by gravity from a can some distance 
away from the furnace. On this pan evaporation of the petroleum took 
place after the furnace was in operation. ‘Several inches above the pan, 
the whole cross-section of the shaft was filled with broken firebrick so 
as to bring about the mixture of the petroleum vapors with the air 
blown in. 
‘oe 
ry 
Fig. 29. Ball mill for grinding samples of cement. 
Above this compartment the third compartment was formed by a 
grating of bricks. At first magnesite bricks were used, later porous 
bricks from a mixture of 80 per cent. magnesite and 20 per cent. of 
Portland cement were employed. On this grating the balls of cement 
mixture were heaped up to the top of the compartment which had 
a height of 8 inches. ‘The cover consisted of a perforated clay tile upon 
which were piled broken. bricks, so as to keep the heat from rushing 
out too rapidly. The clinker compartment was accessible from the out- 
side by means of a door, which was closed by a firebrick plug which 
could be removed and the clinkers withdrawn and examined. 
