32 HUMBLE CREATUEES. 



their form until the rain and thaws of winter spread 

 the matter unifomily over the surface. The worm is 

 unable to swallow coarse particleSj and as it would 

 naturally avoid pure or caustic lime, the finer earth 

 lying beneath the cinders, burnt marl or lime, would 

 be removed by a slow process to the surface. This 

 supposition is not imaginary, for in the field in which 

 the cinders had been spread out only half a year 

 before, I actually saw the castings of the worms 

 heaped on the smaller fragments. Nor, I repeat, is 

 the agency so trivial as at first it might be thought, 

 the great number of earthworms, as every one must 

 be aware who has ever dug in a grass-field, making up 

 for the insignificant quantity of the work which each 

 performs. 



" On the idea of the superficial mould having been 

 thus prepared, the advantage of old pasture-land, 

 which, it is well known, farmers in England are par- 

 ticularly averse to break up, is explained, for the 

 length of time required to form a thick stratum must 

 be considerable. In the peaty field, in the course of 

 fifteen years, about 3| inches had been weU pre- 

 pared; but it is probable that the process is con- 

 tinued, though at a very slow rate, to a much greater 

 depth. Every time a worm is driven, by dry weather 

 or any other cause, to descend deep, it must bring to 

 the surface, when it empties the contents of its body, 

 a few particles of fresh earth. Thus the manures 

 added by man, as well as the constituent parts of the 

 soil, become thoroughly mingled, and a nearly homo- 



