36 
the tent is rolled when taken from the tree. Side guy^ropes are at- 
tached to the bottom of the tent and run through pulleys at the upper 
corners of the scaffold. They are used to open the tent when it is to 
be dropped over the tree, and to fold it up when it is removed. The 
lightness of the apparatus allows of its being easily removed by two 
men, who operate the whole. If necessary, two or more tents can be 
handled by the same scaffolding, one tent being left over the tree while 
the scaffolding is moved to the next. 
In adjusting the tent, the bottom is placed on the ground about 3 
feet from the tree and covered with earth. This brings the gas to bear 
upon the base of the tree and the surrounding soil. 
The Generator in which the gases were produced consists of a heavy 
sheet-iron cylinder, 11 inches in diameter and 13 inches high. The 
bottom rests on a plank, an d to the top is fitted a movable cover sus- 
pended in a frame by a bench-screw. Into the cover are fitted two 
pieces of gas-pipe, one for the exit of the gas toward the tent and the 
other, connected with a pump, carries the gas which returns from the 
tent. Two small reservoirs are also inserted in the cover ; in these are 
contained the solutions which are to flow into the generator for the 
production of the gas. 
In order to establish circulati on and to force the gas into the tent, a 
pump is used which also serves to exhaust the gas from the upper part 
of the tent and to force it again through the generator. It is proposed 
to replace the pump by a small fan-blower, which is much more expe- 
ditious than the common pump which was used. 
THE GASES EXPERIMENTED WITH. 
Among the gases used were chlorine, sulphureted hydrogen, am- 
monia, carbon bisulphide, carbon monoxide, carbonic acid, hydrocyanic 
acid, and carbolic acid vaporized by heat. 
Chlorine . — Some preliminary experiments were made in small vessels 
into which this gas had been introduced. Some infested branches were 
allowed to remain in them for times varying from five to thirty-five 
minutes without any noticeable effect being produced on the insect. 
Atmospheres more strongly saturated with the gas proved fatal to tbe 
insect in a short time. In other treatments extending over eighteen 
hours, with less saturated atmospheres, only a small percentage of the 
insects was killed. No decided effects were noticeable on the foliage 
unless the gas was very concentrated. 
Carbon Bisulphide . — A lime tree, 12 feet in diameter of top, was treated 
with the vapor of 2J pounds of sulphide of carbon for forty-five min- 
utes. At the end of this time the insects were lively, and during the 
treatment had crawled up and collected around a rope surrounding the 
tree at the point where the gas was being injected from the hose. It 
proved that the gas thus used injures neither the insects nor the foliage. 
