GRIMSLEY: GYPSUM IN KANSAS. 25 
Such a kettle holds seven and one-half tons of ground rock, which 
is calcined in three hours. It loses about one-fourth its weight 
through loss of water, which passes out the vapor stacks connected 
with the kettle, so that there remains about six tons of plaster. 
During the process of calcination the whole mass is stirred by a 
revolving stirrer, making about fifteen revolutions per minute. 
Plan of rxe Caleining Kettle ———_—— 
Seale I'e/ Lrsam Uach Co Eitoprrse Hong 
Figure 6. Gypsum Calcining Kettle, 
