SOIL OR SURFACE-MATTER. 239 



than two square feet in superficial area, and sometimes 

 exceeds a square yard, the yearly work done by a 

 number of colonies must be very considerable. The 

 ants that build in the sandy moors seem to frequent 

 the same spot year after year ; and some of the 

 hillocks, after a number of years, are of a consider- 

 able height ; some that were measured in the County 

 Cork being four feet high, and nearly a yard in 

 diameter at the base. The ants that build on rocks 

 appear to occupy generally new places every year; 

 but perhaps not always, as it has been observed that 

 in some places the new work has been carried on 

 in a place where other works had existed in former 

 years. The rock-covering ants are undoubtedly the 

 most useful animals of the two; but the others have 

 also a serviceable place in nature, as they change a 

 cold unprofitable peat into a workable vegetable soil. 

 Other soil-producing animals in these countries 

 are moles, rabbits, rats, mice, foxes, badgers in fact, 

 all animals that burrow in the ground, including the 

 " tillers of the ground." Some do a considerable 

 quantity of work, while others only act in a small 

 way. Moles are among the most active workers ; so 

 are rabbits; the latter often in a great measure helping 

 to change cliffs into sloping escarpments ; while foxes 

 and badgers in general do very little work, as they 

 will rather occupy natural holes than burrow for 

 themselves. 



