MILLS AND OTHER BUILDINGS 167 
house during the process of fumigation. It has re- 
cently been applied in a room of the Division of 
Botany, United States Department of Agriculture, by 
W.R. Beattie, for the destruction of cockroaches. He 
recommends the use of the gas at the rate of 0.10 to 
0.22 gramme cyanide per cubic foot for the destruc- 
tion of flies, cockroaches, moths, etc. For fleas and 
bedbugs the writer has found that a dose varying from 
0.20 to 0.22 gramme cyanide per cubic foot is far more 
desirable. 
This method will be found very useful in clearing 
large hotels, dwelling-houses and other buildings used 
as summer resorts of undesirable pests. The gas 
should be applied at a time when the buildings are 
not occupied. On account of its very rapid diffusion, 
from three to twenty-four hours will accomplish the 
desired results. No fumigation for less than three 
hours is recommended for household pests. Under no 
circumstances should it be used in a house or other 
building occupied by other individuals, either above, 
below, or on either side of the room or apartment 
fumigated. The gas will in no way injure any article 
of furniture found in the ordinary household. Care 
should be taken, however, to remove all edible mate- 
rials. Water used for drinking should not be left in 
the room. ‘The gas should not be handled by persons 
who are not thoroughly familiar with its deadly na- 
ture. It is, therefore, not generally recommended for 
use in houses unless applied by an expert. 
Explosive properties.—In all our experiments and 
recommendations we have kept the amount of potas- 
sium cyanide considerably below the danger limit, so 
