60 DIVERSIONS OF A NATURALIST 



those who He on that beach in the sunshine, and, for 

 want of something better to do, turn over handful after 

 handful of its varied material. And, besides all the 

 stones I have already mentioned, they find amber, 

 washed here by some mysterious currents from the 

 Baltic, wonderful fossil shells out of the crag, the 

 cameo shell, and the great volute, shells which are 

 as friable as the best pastry when dug out of the Red 

 Crag, but here on the shore become hardened by 

 definite chemical action of the sea-water, so as to be 

 as firm as steel. Here, too, the " chiffonier " of the sea- 

 shore finds recent shells, recent bones (slowly dissolving 

 and wearing away), well-rounded bits of glass, jet 

 drifted down from Whitby, Roman coins, bits of Samian 

 ware (!), mediaeval keys, bits of coal, burnt flints (from 

 steamers' furnaces), and box-stones. 



A very important and interesting thing about 

 " beaches " is the way in which the pebbles of which 

 they consist are assorted in sizes. Suppose that one 

 prepares a trough some two or three yards long and 

 twelve inches deep, and lets it fill with water from a con- 

 stantly running tap, tilting it slightly so that the water 

 will overflow and run away at the end farthest from the 

 tap. Then if one drops into the trough near the tap 

 handful after handful of coarse sand and small stones of 

 varied sizes, they will be carried along by the stream, 

 and the more rapid and voluminous the stream the 

 farther they will be carried. But they will eventually 

 sink to the bottom of the trough, the bigger pieces first, 

 then the medium-sized, then the small, and the smaller 

 in order, as the current carries them along, so that one 

 gets a separation and sorting of the solid particles 

 according to size, a very fine sediment being deposited 

 last of all at the far end of the trough. The waves of 



