30 HYDROCYAXTC-ACID GAS FUMIGATION IN CALIFORNIA. 



For instance, suppose that on the line over the center of the tree 12 

 is nearest the ground on one side and 15 on the other. The distance 

 over the center of this tree would be the sum of these numbers, which 

 is 27 feet. With the lines graduated after this manner it makes little 

 difference in determining the distance over the top of the tree whether 

 or not the geometrical center of the tent is at the center of the tree, 

 the single requirement being that some part of one of the graduated 

 lines approximates the center of the tree. 



The two lines running parallel to this central line- should be about 

 4 feet distant from it in the larger fumigating tents. The reason for 

 using these auxiliary lines is, that in practice the center of the tent 

 is very often pulled considerably to one side, especially in covering 

 small trees. If the middle line does not fall immediately over the 

 center of the tree, one of the other two lines is quite likely to do so, 

 and that one should be used in obtaining the distance over. 



The cross line running at right angles to the three parallel lines also 

 passes through the center of the tent and is marked like the others. 

 The idea of this cross line is that in case of an irregularly shaped 

 tree the distance over can be taken in two different directions and the 

 average taken for use in determining the cubic contents. For experi- 

 mental purposes with a few tents this line is an advantage, but in 

 practical operations it is unnecessary and should never be placed on 

 the tent, as measurement over the top in one direction is sufficient. 

 The presence of so many lines tends to confuse the operator. 



Having calculated the volume of a tree from the two measurements, 

 around and over, it is possible to dose the tree at any strength per 

 unit volume desired. When the dosage has been determined the 

 chemicals are measured out and placed underneath the tented trees. 



THE OLD METHOD OF PROCEDURE. 



When this investigation was started, a system of fumigation was 

 used exclusively in which the dosage given the trees was based 

 entirely on guesswork. The estimator, who ordinarily is the man in 

 charge of the outfit, starts out in an orchard equipped with a blank 

 schedule sheet of cross-section paper. He walks between two rows 

 of trees, jotting down in the corresponding squares of the schedule 

 sheet the dosage which he believes the trees should receive. This 

 dosage is based on his eyesight supported by his past experience. 

 If he is a careful scheduler, he will look at the trees from different 

 sides before indicating the dosage, as trees are sometimes more com- 

 pact on one side than on another. Less careful men set down the 

 dosage for the two rows of trees while moving along as fast as they 

 can walk. The writer has seen some schedulers walk through the 

 orchard at a rapid j)ace, taking four rows at a time. 



