The third layer seems to show, from the limestone and the fresh-water
shells embedded in it, that the level land where the forest grew sank lower
and lower until it formed a hollow which in time became a lake.
The fourth layer, which "ends this strange, eventful history," gives
evidence of the whole land having been again covered by the ocean, and
again raised above the waters!
If we were studying geology together, I should like to take you with me to
the Museum, and we would first look at the fossils which are believed to
belong to the most ancient time of life upon the earth; then we would pass
on to those belonging to the second or "middle" stage, and then to the
third, or "new" stage, letting these wonderful stones, taken from mountain
height or deep sea bottom, or from the depths of the earth itself, tell
their own eloquent story.
But what I should like you to remember is that geologists of our own time
tell us that the lowest layer of the earth's crust which has yet been
explored appears to be made of vegetable remains, so crushed and altered by
time and by the tremendous pressure of rocky layers lying above it,
that though it is probably of the same material as that which forms the
coal-measures, it resembles the blacklead of which pencils are made much
more than the coal which you know is what has been formed by the decay of
buried forests and jungles.
In this layer of "graphite," geologists with the help of their microscopes
have searched in vain for any trace of what once was living, but they think
it may have been formed from the "flowerless" plants, or even from those
still more lowly, too minute when living to be seen by the naked eye, and
consisting of one tiny bag or "cell.
Pages:
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215