80 



THE GEOLOGIST. 



" As the worms desert their old burrows, the soil sinks in and fills them ; 

 and by this means a constant circulation is continued, the vegetable mould ex- 

 tending itself downwards, while the * dead soU '—that is, the purely mineral 

 jnatter — is brought up, and so the cultivable staple increases. If we examine 

 even the unmoved gravel in the pit, wherever it is not too deep below the 

 surface, we shall find that the worms are invading it, eating out the sand 

 between the stones, running their excavations down in favourable places, 

 plastering them, too, round the sides with the peculiar slime and earthy matter 

 with wiiich they puddle them to keep out the wet, and leaving their excrement 

 in them ; thus gradually changing the colour of the mass, and making it fit for 

 the roots of the herbage above to strike into. 



" It is believed to be a mistake, however, to suppose that the growing vege- 

 tation is supported chiefly by vegetable decay. A certain essential portion of 

 its carbon — that is, its vegetable matter — the rising plant, it is thought, must 

 thus obtain ; but it is dependent upon the atmosphere for its chief supply, 

 having the power of elaborating carbon from it by means of its leaves. What 

 the plant specially wants from the soil is mineral matter ; and this the earth- 

 worm keeps withm its reach, by continually transferring it from below upwards, 

 in a properly comminuted state. Every shower that falls washes away some of 

 this valuable matter, as anyone may see who wiU watch the riUs which trickle 

 over the surface at the time ; and if the rain is heavy, it carries off a great 

 quantity of clay and sand. The unavoidable consequence of this natural 

 operation would be that the upper layer would consist chiefly of the coarser 

 materials, the larger grit and stones, which would be ill adapted for the sup- 

 port of the more valuable kind of herbage. But the earthworm supplies the 

 waste; and in this way is an agent of which geology must take notice; 

 for denudation and its consequences — ^the fiUing up of valleys and lakes, the 

 growth of deltas at the mouth of rivers, and the accumulation of strata on the 

 sea-bottom — would all go on more slowly if the worm did not bring up fine 

 matter to the surface for the rain to sweep ofP." 



We have not space in this number to notice very minutely Mr. Eley's book ; 

 and indeed it is not essential that in reviewing we should descend into parti- 

 culars. It win suffice then to add a plan of the work. From the flint-pebbles 

 in his garden our author passes to a consideration of the Chalk formation and 

 the great physical changes to which the Wealden area of the south-east of 

 England has been subjected. 



In treating of the origin of those remarkable bands of siKceous nodules which 

 mark the upper beds of our English chalk, however, Mr. Eley throws no addi- 

 tional light, and leaves that difiicult question as he found it. 



Erom the physical events of this region we are passed on to the boulder-drift 

 and to still jnore expanded views of the general physical conditions of our 

 globe itself. Then are so naively brought forward the habits and operations 

 of the earth-worm to which we have so pointedly alluded. The concluding 

 chapter dcvelopcs the author's view that the changes indicated by Geology 

 reveal part of a fore-ordained plan for preparing the earth's sui-face for the 

 occui)auoY of man. Eor om'selves we have derived both pleasure and instruction 

 Iroiu Mr. Eley's book, and there are but few which it has fallen to oui- lot to 

 rracl, I liat we could recommend to our readers so sincerely, or with so much 

 pleasure. 



