18 
FUMIGATION INVESTIGATIONS IX CALIFORNIA. 
threads twisted hard and woven fairly close. This double-twisted 
material is heavier and much stronger than the special drill, but not 
so closely woven; consequently it is somewhat more porous. In 
field work the special drill will adapt itself more closely to the 
irregularities of the ground than the army duck, and particularly if 
the tents become damp. The special 6^-ounce drill is generally con- 
sidered the best 
obtainable for use 
in all fumigation 
tents up to 45 
feet standard size. 
Special 8- ounce 
army duck is rec- 
ommended for 
use in tents of 
larger size. Prob- 
ably the most sat- 
isfactory method 
of making large 
tents is to have 
the center of spe- 
cial duck and the 
sides of special 
drill. This dis- 
tributes the heavy material at the points of greatest wear, while the 
drill makes the tent much lighter and more flexible. 
Fig. S.— Tray commonly used for carrying the chemicals of fumigation 
from tree to tree. Cans above contain cyanid; pitchers below contain 
acid. (Original.) 
POIXTS OX PROCEDURE. 
The number of men making up an outfit varies from three to six. 
In San Bernardino County most of the outfits consist of six men; else- 
where they more commonly consist of four. 
In estimating the dosage, the usual method is to make the estimate 
before the trees are covered with a tent. Sometimes this scheduling 
is done in the daytime, sometimes by night. The schedule for a row 
of trees to be fumigated having been given, either one of two methods 
of procedure is followed. In the first and more common method the 
dosage of cyanid and acid for each tree of the row is measured out 
into small cans and pitchers, which are placed in a tray after the man- 
ner shown in figure 8. When ready for use this tray is carried from 
one tree to the next down the row (fig. 9). Frequently two trays are 
necessary to carry the material required for the entire row or set of 
trees. The water is carried in a pail and measured at each tree. 
The receptacles in which the gas is generated consist of earthenware 
jars holding 1J to 2 gallons, having the handle on the side (fig. 10). 
If dosages in excess of 16 ounces are used in a U-gallon generator or 
