28 



DISTRIBUTION OF ORGANIC REMAINS 



at the top, have not unfrequently been mistaken for trees that have 

 the true woody structure. 



The progressive development and succession of more perfect 

 forms, as we ascend from the ancient to the most recent strata, ap- 

 pears confirmed by the fossil remains both of animals and vegetables. 

 These remains afford a mass of positive concurrent evidence that 

 cannot be refuted by negative arguments. We are told, that the bed 

 of the sea has not been dredged, to discover what species of animals 

 have existed in former ages. The geologist can have no need of 

 such an operation. If the bottom of the sea has not been dredged, 

 it has been laid bare, and is now exposed, over an extent equal to 

 that of the habitable globe. For every island and continent has form- 

 ed part of an ancient bed of the ocean, and that not only once, hui 

 repeatedly and at distant epochs. This extended surl^ace of the bed 

 of the ancient ocean, is exposed to the examination of thousands 

 of observers in every degree of latitude, not covered by polar snows. 

 These examinations have hitherto confirmed the position (taken with 

 certain limitations) that a progressive development of more perfect 

 organic forms, both in the anime] and the vegetable kingdoms, may 

 be traced, from the most ancient rocks in which these remains ap- 

 pear, through the different classes of rock, until we ascend to the 

 most recent, which contain remains of animals analogous to existing 

 species. All or nearly all the instances that have been cited of ani- 

 mals of the higher classes being found vn ancient strata have proved, 

 on further examination, to be fallacious ; yet when we consider what 

 disturbing causes have acted on the crust of the globe, it need not 

 appear surprising if recent species of aninaals should sometimes be 

 found buried in the lower rocks : this, however, would not affect the 

 present question. The subject will be referred to In a subsequent 

 chapter. 



In fossil vegetables, the original vegetable matter is, often, so com- 

 pletely removed, that no trace of it is visible, and the stem appears 

 converted into ironstone, sandstone, or chert. In some instances, the 

 surface of the stem is black and carbonaceous, and all the inner 

 part is mineralized. Sometimes, even when the stem is completely 

 silicified, the vegetable organization is still perceptible, and some 

 traces of the vegetable principles may be obtained, by distillation. 



As most of the vegetable remains found, both in the secondary and 

 tertiary strata, are analogous to the plants of tropical climates, it has^ 

 been inferred that the temperature of the globe was, once, consider- 

 ably higher than at present. It cannot be denied, that there are ma- 

 ny geological phenomena which strongly favour this conclusion : there 

 are, however, some striking facts which seem opposed to it. The 

 consideration of this question will, therefore, be resumed in another 

 part of the present volume. 



