These layers, beginning at the bottom, are as follows; (1)
igneous granite, unstratified; (2) limestone laid down from life in the
ocean, metamorphosed by heat and all fossils thereby destroyed; (3)
limestone highly crystallized, composed of fossil shells and very hard;
(4) sandstone, made under the sea from previous rock powdered, having
huge concretionary masses with a shell or a pebble as a nucleus around
which the concretion has taken place; (5) shale from the sea also; (6)
conglomerate, or drift, deposited by ice in the famous glacial cold
snap; (7) alluvium soil deposited in fresh water and composed partly of
organic matter. In our second illustration some of these layers, or
strata, may be distinguished.
[Illustration: The Work and the Worker, Santa Cruz, Cal.]
When the awful blows of the sea smite the rock, if it finds a place
less hard than others, it wears into it a slight depression, after half
a hundred thousand strokes, more or less, and ever after, as the years
go by, it drives its wedges home in that place. A shallow cave
results. Then the waters converge on the sides of the cave and meet
with awful force in the middle. Thus a tunnel is excavated, like a
drift in a mine, each wave making the tremendous charge and the
reflowing surges bringing away all the detritus. This tunnel may be
driven or excavated two hundred feet inland, under the shore.
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