STRATIFICATION 263 
is changed to another place, the material deposited is 
that which the waves furnish. 
Another way in which these small variations may 
be caused, is by the ordinary changes of weather, from 
quiet to storm, and from the moderate summer to the 
extreme conditions of winter. When waters are agi- 
tated by waves, and moved by the wind currents that 
storms produce, the fine particles of sediment are 
floated away from the muddy coast, and only the 
coarser allowed to settle to the bottom; but when 
the water is stiller, the coarser fragments are either 
not supplied or else not transported so far, and in 
this case the sediments are partly, if not entirely, 
made of fine fragments which build a layer of mud. 
Therefore, as a result of this difference in rate of 
movement of the water, the texture of the beds may 
vary. On one day mud may settle, during the next 
a layer of sand, and on the following these two layers 
may be covered by a thin deposit of pebbles; and so, 
from day to day, the accumulation on the ocean bottom 
near the shore, may be made to vary considerably. In 
winter the water is on the average roughened more 
than in summer, and hence the deposits that accumu- 
late during the winter season, will in general be coarser 
than those made during the summer. 
Greater variations. To account for the larger beds 
or strata, more permanent changes are necessary. 
