2 FUMIGATION METHODS 
Department of Agriculture for 1887, and in ‘‘ Insect 
Life,’’ Vol. III., by way of explanation, he wrote me 
March 21, 1898, as follows: ‘‘ During the summer of 
1886 I was employed by the United States Depart- 
ment of Agriculture to carry on a series of experiments 
at Los Angeles, California, against the cottony cushion 
scale (/eerya purchasi), but owing to an insufficient 
appropriation I was laid off on August 1st of that 
year. As no perfect remedy had at that date been 
discovered, I determined to experiment with gases 
in a private capacity and at my own expense. 
Accordingly, during the first week of the following 
month I began experimenting with hydrocyanic acid 
gas, which I thought would be the best for the pur- 
pose, owing to its very poisonous qualities, the rapidity 
of its generation, and the readiness with which it dif- 
fuses itself in the air. Nobody suggested to me to 
try this gas. It was not until the following July that 
the Department of Agriculture again placed me on its 
rolls.”’ 
It will thus be seen that Mr. Coquillett continued 
to work on the problem of destroying the scale, though 
at his own expense, and in September, 1886, began 
seriously to study the methods of fumigation. Fumi- 
gation with carbon bisulphide had been inaugurated 
on a small scale by J. W. Wolfskill and his very able 
foreman, Alexander Craw, at Los Angeles. At their 
place Mr. Coquillett began his experiments, profiting 
by the facilities here provided. It was here he first 
conceived the idea of using hydrocyanic acid gas. 
About six months were required to perfect methods. 
The result of the work in the Wolfskill orchards 
