I am now going to tell you, my young friends, about some of the wonderful things in the earth, sea, and sky. A great number of them I have seen myself in my travels through various countries, and others I have only read of; but I shall tell you nothing that is not strictly true, for I do not wish so much to astonish you as to make you I shall begin with some of the wonders of the earth which, as I suppose you know, belong to the branch of natural history which is called geology; and to enable you to understand what follows, I must first explain how the materials which compose the ground you tread upon are arranged. If you hastily travel over any extensive tract of country, such as that between New York and Philadelphia, or between London and Bristol, you might think that all the different substances, clay, chalk, limestone, and granite, were irregularly mixed together. This is, however, not the case, when taken on a great scale; for if you more carefully examine, you will find that the various sorts of earth are disposed in layers, or strata, and that a uniform order of arrangement is nearly preserved. If these layers were perfectly horizontal, laid one over another like the coats of an onion, we But, instead of this, the surface is broken up by some force from beneath elevating portions, so as to form mountains and hills; and in consequence of this the edges of the strata appear on the surface one after another; just as you would see the edges of a row of bricks that had been set up on their ends, and then the last one thrown down so as to push down all the others. This is the way in which the strata are placed in the neighbourhood of Weymouth. The chief reason why I wished you to understand this is, that you may see how it is known that one stratum is older than another. It is evident that the substance marked a, in the section, which is limestone, must have been deposited before b, while b must certainly be older than c. Now in most of the strata above the granite, which is nearly always in the position of the oldest formation, there are found various shells, plants, and bones of animals; and where certain remains of different animals or vegetables are found in one stratum, it is concluded that they must have been living about the same time. Most of the animals of the older strata were different in form from any at present known to exist; and some of them are very remarkable, and if they were alive now, would seem to us very strange and awkward. EXTINCT ANIMALS. |
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