CONSTRUCTION OF VENTILATORS AND FLOORS I1I7 
the cyanide dropped in. The trap-door is closed 
quickly and is covered immediately with a piece of 
cloth (blanket is best), and dirt hurriedly thrown 
over the whole business. This prevents any of the 
gas from escaping, and makes the building absolutely 
air-tight, which is necessary. The gas fills the exca- 
vation and rises through the loose floor, permeating 
through the trees, filling the entire inside of the 
house. In our building we treat about five thousand 
trees ata time. For fall deliveries we treat the stock 
as it comes from the field to the packing-ground. For 
spring delivery we treat them as we take them from 
the healing grounds to the packing-grounds. The 
cost of our building did not exceed $50 complete.’’ 
