THE CONSTITUENTS OF A SEABEACH 63 



also deposited, together with still finer particles (those 

 called " mud "), on the shallower parts of the sea bottom. 

 The curious thing about the particles of " sharp " sand 

 is that they are angular, and for the most part without 

 rounded edges. If you examine them under a micro- 

 scope you will see that they do not look like pebbles — 

 in fact, they are not pebbles, for they are so small and 

 have so little weight, or, rather, mass, that they do not 

 rub each other to any effect when moved about in water. 

 They look like, and, in fact, are, for the most part broken 

 bits of silica, unworn and sharp-edged splinters and 

 chips, glass-like in their transparency and most of them 

 colourless, a few only iron-stained and yellow. Amongst 

 these are a few rounded, almost spherical pieces, which 

 are no doubt of the nature of minute water-worn pebbles. 

 Although these few minute pebbles exist among the 

 sharp, chiplike particles of "sand," it is clear that we 

 must broadly distinguish " pebbles " of all sizes down to 

 the smallest— from the much smaller "sand particles." 

 There is no intermediate quality of material between 

 " sand " and the finest " shingle." 



