THE LEVELLING POWER OF RAIN. 



IT has been recognized, ever since geology has become truly 

 a science, that the two chief powers at work in remodelling 

 the earth's surface, are fire and water. Of these powers one 

 is in the main destructive, and the other preservative. Were 

 it not for the earth's vulcanian energies, there can be no 

 question that this world would long since have been ren- 

 dered unfit for life, at least of higher types than we recog- 

 nize among sea creatures. For at all times igneous causes 

 are at work, levelling the land, however slowly ; and this not 

 only by the action of sea-waves at the border-line between 

 land and water, but by the action of rain and flood over 

 inland regions. Measuring the destructive action of water 

 by what goes on in the lifetime of a man, or even during 

 many successive generations, we might consider its effects 

 very slight, even as on the other hand we might underrate 

 the effects of the earth's internal fires, were we to limit our 

 attention to the effects of upheaval and of depression (not 

 less preservative in the long run) during a few hundreds or 

 thousands of years. As Lyell has remarked in his " Principles 

 of Geology," " our position as observers is essentially un- 

 favourable when we endeavour to estimate the nature and 

 magnitude of the changes now in progress. As dwellers on 

 the land, we inhabit about a fourth part of the surface ; and 

 that portion is almost exclusively a theatre of decay, and not 

 of reproduction. We know, indeed, that new deposits are 

 annually formed in seas and lakes, and that every year some 



