334 THE CAUSES OF THE xi 



existence to the consideration of the history of the 

 formation of mud ! But, in Nature, there is 

 nothing mean and unworthy of attention ; there is 

 nothing ridiculous or contemptible in any of her 

 works ; and this inquiry, you will soon see, I hope, 

 takes us to the very root and foundations of our 

 subject. 



How, then, is mud formed ? Always, with 

 some trifling exceptions, which I need not consider 

 now always, as the result of the action of water, 

 wearing down and disintegrating the surface of 

 the earth and rocks with which it comes in 

 contact pounding and grinding it down, and 

 carrying the particles away to places where they 

 cease to be disturbed by this mechanical action, 

 and where they can subside and rest. For the 

 ocean, urged by winds, washes, as we know, a long 

 extent of coast, and every wave, loaded as it is 

 with particles of sand and gravel as it breaks 

 upon the shore, does something towards the dis- 

 integrating process. And thus, slowly but surely, 

 the hardest rocks are gradually ground down to a 

 powdery substance ; and the mud thus formed, 

 coarser or finer, as the case may be, is carried by 

 the rush of the tides, or currents, till it reaches 

 the comparatively deeper parts of the ocean, in 

 which it can sink to the bottom, that is, to parts 

 where there is a depth of about fourteen or fifteen 

 fathoms, a depth at which the water is, usually, 

 nearly motionless, and in which, of course, the 



