Page 98 - The snake's pass

86 THE SNAKE S PASS.
not go into the matter thoroughly, for that old wolf of
mine was so manifestly impatient that I should get to
his wild-goose chase for the lost treasure-chest, that
the time and opportunity were wanting. However, I
saw quite enough to convince me."
" Well, how do you account for the change ? What
"
is your theory regarding the existence of limestone ?
" Simply this, that a lake or reservoir on the top of
a mountain means the existence of a spring or springs.
Now springs in granite or hard slate do not wear away
the substance of the rock in the same way as they do
when they come through limestone. And moreover,
the natures of the two rocks are quite different. There
are fissures and cavities in the limestone which are
wanting, or which are at any rate not so common or
perpetually recurrent in the other rock. Now if it
should be, as I surmise, that the reservoir was ever fed
by a spring passing through a streak or bed of lime-
stone, we shall probably find that in the progress of
time the rock became worn and that the spring found
a way in some other direction—either some natural
passage through a gap or fissure already formed, or by
a channel made for itself."
"
" And then ?
" And then the process is easily understandable. The
spring naturally sent its waters where there was the
least resistance, and they found their way out on some
level lower than the top of the hill. You perhaps
noticed the peculiar formation of the hill, specially on