74 



not expensive when bought in quantity, requires no mixing or 

 apparatus for application, can be used by anybody with ordi- 

 nary caution, as its strong odor, like that of rotten eggs, 

 immediately gives warning of danger, and is sure death to rats 

 and to most other burrowing animals if properly used under 

 right conditions. It should never be used in or about buildings 

 where there is fire, as it is both inflammable and explosive. In 

 the woods or fields it should be used after a heavy rain, or in 

 winter or spring when the ground and grass are wet. Then 

 there will be no danger of setting fire to grass or dead leaves, 

 and the gas will be more deadly than when the soil is dry, as it 

 wUI remain in the burrows instead of being dissipated through 

 the minute crevices of the soil. 



The following method of applying the gas as used at 

 Thompson's Island was very effective, as it killed practically 

 all the rats in about 400 holes, where it was used experi- 

 mentally. There the rats burrow in the banks around the high 

 coast of the island, and many of them live in the burrows all 

 the year, as they can find shellfish, garbage, etc., on the beach 

 below throughout the winter, unless the harbor is frozen over, 

 and they store up more or less food in their burrows. The first 

 step in their destruction is to mark each hole by dropping a 

 little plaster of paris at its mouth, and then to determine the 

 number of burrows occupied. This was done by stuffing the 

 mouth of every hole full of grass or seaweed. If a burrow is 

 tenanted the rats are very likely to remove the grass at its 

 mouth within twenty-four hours. In this work the ordinary 

 bee smoker was used as a means of finding all hidden holes. 

 When one hole is found, there are usually others connecting 

 with it, some of which may be unused passages covered by 

 grass, leaves or rubbish which, unless discovered and filled, will 

 allow the gas and the rats to escape. The bee smoker is filled 

 with cotton waste which is set on fire, and the smoke from its 

 smouldering is puffed into a hole to the windward of others, if 

 possible. Soon the smoke is seen issuing from all connecting 

 holes, all of which are then closed with mud or wet earth, 

 except one (the highest, if possible, as the gas readily descends). 

 Then a bunch of cotton waste, grass or similar substance is 

 saturated with one and one-half to two ounces of carbon bi- 



