THE CARBONIFEROUS SYSTEM. 175 
forming. This is proved by the fact that the blackband is fuil of the 
shells of Estheria, a bivalve, aquatic crustacean. We know that at the 
time of the formation of Coal No. 1 rivers flowed down from the north 
into the coal basin, and there is little doubt that a tree uprooted on the 
banks of one of these streams carried with it a fragment of the rocky 
ledge on which it grew. Floating trees, holding stones in their roots, are 
often noticed in our great rivers at times of flood; and I have seen a 
mass of gold-bearing quartz taken from the alluvial deposits of the Mis- 
Sissippi, near Memphis, which must have been brought from Wyoming 
or Montana in the way I have described. 
On the preceding pages I have reviewed the geological structure of our 
portion of the Alleghany coal field. The subject is one of considerable 
interest, and it has been treated somewhat in detail, and yet it is so sug- | 
gestive and fruitful that it is necessarily imperfectly presented in this 
chapter. The reports on the different counties that he within the coal 
area are more properly the media through which details of geological 
structure are described. These are filled with facts which it is hoped 
will serve to make this sketch somewhat more comprehensible than it 
would be if it stood alone. , 
The series of sections of the Coal Measures which I have prepared for 
publication with this volume will, I think, make it, easy to follow the 
descriptions traced, and it is hoped that they will themselves afford evi- 
dence in favor of the truth and fitness of the classification of our coal 
seams which I have adopted, that will be far more satisfactory and influ- 
ential than any argument. I think no one can follow with the eye 
the common elements that run through these sections without being 
convinced that there is more system and harmony in the structure of our 
coal field than some of our writers on the subject have been willing to 
concede. 
I should say further, that the economical aspects of the subject now 
considered—z. ¢., the arrangement, connection, reach, and identity of 
coal seams, as also their chemistry and technology—will form an impor- 
tant part of the volume on Economic Geology, which, in due course, will 
follow next in order to those now published. 
THE FAUNA AND FLORA OF THE COAL MEASURES. 
So much space has already been allotted to the geology of our Coal 
Measures that little remains for their paleontology. But this is a sub- 
ject that belongs properly in another volume, and it will be considered 
there more fully than would be possible in any circumstances here. I 
