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It is the work of the geologist to read the ancient and modern records of the changes of the earth in times past. Even the most casual observer cannot fail to see that the earth of to-day is different from that of yesterday; the earth of this year is still more different from that of last year, and the earth of this century from that of thousands of years ago. Sea shells, imbedded in the rocks of our hills and mountains, teach us that Texas was once beneath the ocean. A careful study will also show that some parts of the State were dry land, while others were under the sea. Those parts which have been the longest dry land, are termed the oldest; for, strictly speaking, no part is older than the other, for matter is eternal, and. what we call new and young is only old matter in a new form.

As this report is intended for the general reader, we give below a synopsis of the principal geological periods already known in Texas, omiting their subdivisions:

The Azoic are igneous rocks, destitute of animal and vegetable matter, thrown up from below, or rocks altered by contact with such melted matter. These last are termed metamorphic rocks. Gneiss, mica schist, etc., are examples of the latter, and granite and its associated crystaline rocks of the former. The metamorphic rocks may have had fossils, which have been destroyed by heat.