ENTOMOLOGY 389 



while simple enough when once understood, warrants a description. 

 The machinery employed consists of two simple uprights, with at- 

 tached blocks and tackle. 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 to- 

 gether 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 triangu- 

 lar 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 octag- 

 onal 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 1%-inch manila rope is sewed about the 

 border of the central piece in an octagonal pattern. Rings are at- 

 tached 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 fas- 

 tened, and the tent is elevated over the trees and handled with com- 

 parative ease. 



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 bv spontaneous combustion un- 

 less carefully watched until the oil is clry. A much better material 

 than oil is found in a product obtained from the leaves of the com- 

 mon prickly pear cactus, which grows in abundance in the South- 

 west. The liquor is obtained by soaking chopped-up leaves in water 

 for twenty-four hours. It is given body and color by the addition of 

 glue and yellow ocher or Venetian red", and is applied to both sides 

 of the canvas and rubbed well into the fiber of the cloth with a 

 brush. 



