8 



inches of cotton seed. The failure of a heavy application of the gas 

 to kill house flies covered by from 6 to 12 inches of seed in five hours 

 shows the great resistance of bulk cotton seed to the uniform diffusion 

 of hydrocyanic acid gas. It was consequently considered that there 

 was not a promising outlook for this gas on account of its very slight 

 penetrating power, and attention was directed to carbon bisulphid. 



Experiment with carbon bisulphid in box of 15.88 cubic feet capacity . 



This experiment was performed in a tight box, in which were placed 

 sacks of cotton seed containing weevils in perforated tin boxes buried 

 at varying depths, as in the preceding experiment. The amount of 

 carbon bisulphid used was varied from 1^ pounds per 1,000 cubic feet, 

 a rather heavy application for the destruction of insects in stored 

 grain, to 5 pounds per 1,000 cubic feet. It will be noted that the 

 insects covered by 10 or more inches of seed were not killed in twenty- 

 four hours, even with the heaviest application. However, it was con- 

 sidered advisable to verify these results by another experiment, as 

 follows: 



Experiment with carbon bisulphid in cylinder 70 inches long. 



This experiment was performed in an upright, gas-tight, galvanized- 

 iron cylinder 70 inches long by 12 inches in diameter, in order to 

 obtain conditions similar to those existing in the case of cotton seed 

 stored in bulk or in bins. The carbon bisulphid was placed in a shal- 



209 



