37 
about 75 cents per tree. It is not practicable to treat trees above 30 
feet in height. 
The handling of the bell tents is simple and needs no further de- 
scription, but the large tents are not so easily operated, and the 
method of adjusting the great flat octagonal sheets over the trees, 
while simple enough when once understood, warrants a description. 
The machinery employed consists of two simple uprights, with at- 
tached blocks and tackle (fig. 7). The uprights are about 25 feet 
high, of strong Oregon pine, 2 by 4 inches, and are provided at the 
bottom with a braced crossbar to give them strength and to prevent 
their falling to either side while the tent is being raised. A guy 
rope is attached to the top of each pole and held to steady it by a mem- 
ber of the crew stationed at the rear of the tree. The tent is hoisted 
by means of two ropes 70 feet long, which pass through blocks, one 
fixed at the top of the pole and the other free. The tent is caught 
near the edge by taking a hitch around some solid object, such as a 
green orange, about which the cloth is gathered. By this means the 
tent may be caught anywhere without the trouble of reversing and 
turning the heavy canvas to get at rings or other fastenings attached 
at particular points. The two remaining members of the operating 
crew draw the tent up against and over one side of the tree by means 
of the pulley ropes sufficiently to cover the other side of the tree when 
the tent falls. The poles and tent together are then allowed to fall 
forward, leaving the tent in position. Sufficient skill is soon acquired 
to carry out rapidly the details of this operation, so that little time 
is lost in transferring the tents from tree to tree, even when the trees 
approximate the limit in height. A single pair of hoisting poles 
answers for all the tents used. 
Some of the tents employed are of great size, one described by Mr. 
Havens having a diameter of 76 feet. It is constructed of a central 
piece 50 feet square, of 10-ounce army duck. Four triangular side 
pieces or flaps of 8-ounce duck, 10 feet wide in the middle, are strongly 
sewed to each side of the central sheet, forming an octagonal sheet 70 
feet in diameter. About the whole sheet is then sewed a strip of 
6-ounce duck, 1 yard wide. The tent is handled by means of ropes 
and pulleys. A 14-inch manila rope is sewed about the border of the 
central piece in an octagonal pattern. Rings are attached to this rope 
at each of the eight corners thus formed, and also on either side of 
the tent. To these rings the pulley ropes are fastened, and the tent 
is elevated over the trees and handled very much as indicated in fig 7. 
The canvas for the tents, blue or brown drilling or 8 to 10 ounce 
duck, may be rendered comparatively impervious to the gas by 
painting lightly with boiled linseed oil. This has the objection, how- 
ever, of stiffening the fabric and adding considerably to its weight; 
it also frequently leads to its burning by spontaneous combustion 
unless carefully watched until the oil is dry. A much better material 
127 
