214 ReportT orf THE DEPARTMENT OF ENTOMOLOGY OF THE 
periods in which sets of trees were covered, fumigated and un- 
covered in forty minutes. At this rate it was estimated that 
with the same number of men and six fumigators ninety trees 
could have been fumigated in ten hours. Possibly with a set of 
twelve fumigators one operator with a crew of eight men might 
have fumigated one hundred and fifty to one hundred and eighty 
trees in ten hours, but in no case would it be possible for them 
to fumigate two hundred trees in the same time. 
Advantages.—The principal advantages of this style of fumi- 
gator lie in the fact that it is of constant capacity so that the 
operator does not need to guess at size of trees and vary the 
amount of chemicals used for each; that it can be placed around 
a tree and not require a derrick to lift it over the same, as is the 
case with tents and the Emory fumigator; that it contains a 
minimum amount of waste space compared to its size, and can 
be stored in comparatively small space. In addition it has the 
advantage of rarely breaking the trees or rubbing off the buds. 
ESTIMATING CONTENTS OF TENTS OVER TREES. 
The method usually followed in California has been to esti- 
mate the height of a tree and diameter through the foliage, and 
from this the amounts of chemicals to be used are determined 
by tables previously computed. Johnson! has given a similar 
table but there is an error in his method of estimating the cubic 
contents of tented trees with the result that the amounts given 
in the table are in most cases nearly double what they should 
be, providing he intended to use but .20 gram potassium cyanide 
per cubic foot as stated. The amounts given in table show that 
about .40 gram per cu. ft. was used. He gives the following 
rule for estimating contents: “ First, I calculated the contents 
of a cylinder whose height and diameter are the height and di- 
ameter of the tree, then calculated the contents of a sphere 
whose diameter is the height of the tree. Then by taking half 
the difference and adding it to the contents of the cylinder, I 

1Md. Agr. Exp. Sta. Bul. 57, p. 79. 
