325 
anic acid gas. Accordingly, on the morning of the 13th, the work of 
disinfection was commenced. 
The tents used for the purpose of inclosing the infested trees are made 
of 8-ounceduck, oiled with linseed oil. They are in the form of octagonal 
sheets, and are four in number, two of them being 28 feet in diameter, 
while the other two measure 44 feet. These could be placed over the 
trees by hand, or by the use of poles when the trees did not exceed 10 
feet in height, but on larger trees it was necessary to use a sort of tripod 
for the purpose of placing the tents over them. This apparatus con- 
sists of two pine scantlings, each two by three inches thick and twenty 
feet long, fastened together at the upper end by a bolt having a ring 
in place of a head. To this ring is attached the pulley through which 
passes the rope used in hoisting the tent. To the opposite or lower 
end of each of these scantlings is fastened a cross-piece of 6-inch pine 
board, one of the cross-pieces being 18 inches, the other 5 feet long,, 
and having a brace extendiug from each end to the scantling, to which 
it is fastened at a point 5 feet from its base. These cross-pieces serve 
the purpose of keeping the tripod in an upright position, and in actual 
practice were found to be sufficient for this purpose. 
When the tent is to be placed over a tree, it is spread out on one side 
of the tree and the tripod erected on the opposite side and as close to the 
base of the tree as it is possible to get it ; one end of the five-sixteenths- 
inch rope passing through the pulley at the upper end of the tripod is 
furnished with a strong iron hook, which is next hooked into a loop 
attached to the tent, after which the opposite end of this rope is drawn 
downward until the tent is drawn to the top of the tripod ; the foot of 
the latter is moved several feet farther from the tree and the tent again 
drawn over the tree until it will cover the latter, after which the tent 
is allowed to drop over the tree. 
The chemicals used in generating the hydrocyanic acid gas consist 
of fused potassium cyanide of about 58 per cent purity, commercial sul- 
phuric acid, and water, the proportions being 1 ounce by weight of 
the cyanide, a trifle over 1 fluid ounce of the acid, and 3 fluid ounces of 
water. This will be sufficient for 150 cubic feet of space inclosed by the 
tent; by computing the number of cubic feet thus inclosed and dividing 
this by 150 we obtain the quantity of cyanide in ounces and fractions 
that the tree will require, after which it will be comparatively easy to 
ascertain the quantity of each of the other ingredients required by 
bearing in mind that each ounce by weight of the cyanide will require 
slightly over a fluid ounce of the acid and 3 fluid ounces of water. 
Almost any glazed earthenware vessel will answer the purpose of a. 
generator. I used 1-quart pitchers; also an open vessel holding about 
1 gallon, and a 2-gallon jar. The pitchers were large enough for using 
2J ounces or less of the cyanide, but when a somewhat larger quantity 
than this was used the action of the chemicals resulted in throwing 
a portion of them out of the pitcher, thereby occasioning a loss. On 
