ECONOMIC USE OF HYDROCYANIC ACID GAS 3 
was watched with keen interest by those whose trees 
were fast being ruined by the scales. Many growers 
became impatient to know the remedy so carefully 
guarded by the experimenters. Finally, a number of 
horticulturists about San Gabriel asked Prof. E. W. 
Hilgard, of the University of California, for a chemist 
to experiment in their orchards with various gases. 
F. W. Morse was detailed for this work, and found, 
like Mr. Coquillett, that hydrocyanic acid gas was by 
far the most satisfactory. Inthe course of these ex- 
periments certain parties who had witnessed the former 
experiments recognized the odor of gas, and thus the 
secret, so zealously guarded, was given to the public. 
Although discovered and used by Mr. Coquillett and 
his associates six months previous to the announce- 
ment of Mr. Morse, the first general information about 
the gas as an insecticide was given to the public by 
the latter gentleman in a Bulletin (No. 71) from the 
University of California Experiment Station. 
Extensive experiments were continued by Mr. 
Coquillett. In July, 1887, he was again made an 
assistant of the Department of Agriculture, and did 
more than any other person to develop and perfect the 
present methods of fumigation. The main difficulty 
encountered in these early experiments was the inju- 
rious effect the gas had upon the foliage. The injury 
was lessened greatly by the ‘‘ soda process’’ of Morse, 
which consisted in adding ordinary baking soda to the 
cyanide solution, using something like two and a half 
times as much soda as there was cyanide in the solu- 
tion, the result being the production of carbonic acid 
gas, thus diluting the hydrocyanic acid gas. 
