42 THE STORY OF THE EARTH. 



Coloured with oxides of iron. They are shallow- 

 water or shore deposits which show current bed- 

 ding; due to deposition by changing currents, as 

 well as ripple-marks of wave movement, and f 

 prints of animals. 



Clay. 



Any substance which is taken up by moving 

 water BO as to cloud it, is popularly termed mud, 

 and mud when deposited consolidates into clay. 

 Mud banks abound on parts of the coast where 

 clay forms the cliffs, because tidal movement of 

 the water converts the clay into mud. It is 

 Chiefly composed of light Bocculent particles of 

 silicate <>f alumina, which frost tears apart from 

 each other, and the lightest shower moves down 

 a valley. The mud of rivers is carried into the 

 Sea, as far as the fresh water can tloat over the 



an. 'I he Yellow Sea is yellow with the mud 



of the Hoang-Ho. When the Rhine at Bonn is 



turbid and full of water, - r)(MM) part of its weight 

 is mud: but after continued dry weather the sedi- 

 ment falls to ctItV l )arl (,t lnr weight. Thus the 



•nation of seasons may give a laminated char- 

 acter to deposits carried to ti marking the 

 on of years by changes in the deposit, like 



; 3 of gTO^ tli in tin- w o< >d of a I 



Wh( extends parallel to a shore, in con- 



e of denudation of the cliffs, it commonly 



1 i a definite relation to coarser sediments which 



igited nearer to laud. This is seen m the 



1 .;<• percentage of sand, sometimes amounting 

 t i So per < <nt., w hi( h may be sepai 



w ashing. 'I he parti< 

 t remely fine, so thai 1 1 

 ispension for a long tune by moving 



