334 THE CAUSES OF THE ~ <2) 
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 
