138 The Pocket Gopher. 



and in places reaching almost the actual surface, especially 

 where the excavated earth has been thrust out or where the 

 animal has started to dig an exit and later abandoned the work. 

 If the ground is dry the gas is dissipated the more rapidly, 

 so that good results might be expected only when the soil is 

 sodden by recent rains. 



With us, the plan of forcing the gas into the burrows by 

 means of a bellows gave no better results than the methods de- 

 scribed above. The apparatus used for forcing the gas con- 

 sisted of an ordinary two-gallon -kerosene can with a ten-inch 

 hand-bellows connected by a short piece of half -inch hose to the 

 opening at the top of the can. This end of the hose, or a tin 

 tube attached to it, should extend nearly to the bottom of the 

 can, so that the air from the bellows will have to bubble up 

 through the liquid bisulfid on its way to the exit at the spout. 

 The vapor thus formed is led into the burrow by means of 

 another short piece of hose attached to the spout of the can. I 

 have described the apparatus here because some who have 

 used it in localities where there were comparatively few go- 

 phers and the burrows simple, claim that they have rid their 

 farms of the pest by this means. 



In order to give the gas-pumping method a thorough test, a 

 larger quantity of bisulfid was used in repeated experiments 

 than has been recommended when the liquid is simply to be 

 introduced on a wad of cotton. At each opening made into a 

 burrow the bellows was operated four or five minutes, vaporiz- 

 ing from four to seven ounces of carbon-bisulfid. This varia- 

 tion in the amount of liquid vaporized in equal periods of time 

 was due to difference of quantity put into the can before the- 

 series of experiments was begun. The larger the quantity 

 the more gas will be evaporated in a given period. As carbon- 

 bisulfid costs about twenty cents per pound retail, the expense 

 of treating each burrow was therefore from five to eight cents, 

 not counting the time of the operator. A very conservative 

 estimate will place the average cost of attempting to destroy 

 pocket gophers by this method in the alfalfa fields and mead- 

 ows of central Kansas at one dollar per acre for materials 

 alone. Results do not justify this expense. In a series of 

 thirty experiments personally supervised by the writer during 

 the fall of 1906 and spring of 1907 but four were attended 

 with successful outcome, three of these at a time when the 



