200 SUMMARY OF CHAPTER. CHAP. III. 



or other obstacle, as well as any difterence in the 

 hardness of the soil, and he will turn from that side ; 

 if the earth is damper on one than on the other side 

 he will turn thitherward as a better hunting-ground. 

 Nevertheless, after each interruption, guided by the 

 sense of gravity, he will be able to recover his down- 

 ward course and to burrow to a greater depth. 



