THE HALL SCALE ERADICATION PROJECT 13 
in that year have been used two seasons without showing any gas leakage. 
The gas applicators used 1n the early work were similar to those described 
by Fulton and Nelson (6). Later models incorporated improvements made 
by Yust (3) Cig. 8). Tree volumes were calculated from the distance over 
Ficure 9.—Eyvacuating residual hydrocyanic acid gas from a tent at end of exposure period. 
