9 
of it in the atmosphere to prove fatal to insect life. It tends most 
strongly to spread outward and downward on account of its being so 
heavy, and, though it will gradually work upward, its greatest density 
will be at the lowest levels. The usual calculation is to employ one 
pound of liquid carbon bisulphid to each 1,000 cubic feet of space 
treated, whether for the treatment of insects in buildings or for insects 
in the ground. This amount gives an atmosphere, if confined to that 
space, composed approximately of 1 part in 90 of carbon bisulphid 
vapor, which, as we shall see, is a fatal strength in a short time. 
However, where the atmosphere can not be absolutely confined and 
there is considerable opportunity for the vapor to escape, it is fre- 
quently necessary to apply from two to four times that amount, under 
circumstances where there is no danger of killing plant life. 
INSECTICIDAL POWER. 
In 1876 two French investigators, Cornu and Mouillefert, per- 
formed a series of experiments to determine the insecticidal power of 
carbon bisulphid vapor. They were working primarily upon the 
erape Phylloxera, but, in addition to that insect, they experimented 
with caterpillars, butterflies, cicadas, wasps, and plant-lice. In a 
series of five large flasks they produced an atmosphere composed of 1 
part of carbon bisulphid vapor to 12, 30, 60, 120, and 180 parts of air. 
Within each of these flasks grape roots bearing the Phylloxera were 
confined for twenty-four hours, at the end of which time the insects 
were dead in each case. In other experiments in which all of the pre- 
viously mentioned insects were used it was found that in an atmos- 
phere composed of 1 part carbon bisulphid vapor to 90 parts air, all 
insects perished in a few seconds, and that an atmosphere composed 
of 1 part ef carbon bisulphid vapor to 954 parts of air was fatal in 
one and one-fourth hours. The same result is therefore attained by 
a small proportion of the vapor acting through a long time as by a 
large proportion acting fora short time. 
HOW PUT UP AND COST. 
Carbon bisulphid is put up in tight tin cans or iron drums holding 
from 1 to 50 pounds. It may be purchased in small quantities of any 
druggist, at from 25 to 35 cents per pound; but if any considerable 
quantity is to be used, it is much better to buy of some wholesale 
druggist, or, better still, direct from the manufacturers. In the latter 
way it is shipped in 50 pound cans or drums at 10 cents, or even 
less, per pound, with an additional charge for the drums, which are 
returnable at the purchase price; but all freight charges are paid by 
the buyer. 
