ERECT FOSSIL TREES. 445 



dip of the strata. In the direction of the section, a line 

 drawn through the root of the trees is conformable to the 

 inclination of the strata ; and in the direction of the new dip, 

 this is still more plainly the case ; the large spreading roots 

 of Nos. 2 and 5 being quite conformable TO the inclination 

 of the stratum in which they rest ; and the roots of the 

 others are equally so, to the extent to which they are seen, 

 but being less exposed, they are not so evident in this 

 respect. The whole of the stems stand nearly at right 

 angles to the plane of stratification. They are imbedded 

 chiefly in a soft, argillaceous blue shale, but that which 

 surrounds the upper end of No. 1 is of a more siliceous 

 nature. In the same plane as the roots, a thin stratum of 

 coal has been found as far as the excavations have extended. 

 The trees, when discovered, had each a coating of coal, 

 which was so friable that it crumbled to pieces in removing 

 the shale. It is supposed to have been the bark of the trees 

 carbonised, since they now appear completely decorticated, 

 and present various flutings. The largest, No. 1, is about 

 fifteen feet in circumference at its base, seven feet and a 

 half at its top, and eleven feet in height. The next, 

 No. 5, is seven feet and a half in circumference, and two 

 feet and a half in height ; while Nos. 3 and 4 are of smaller 

 size, being respectively three and five feet in height and six 

 in circumference. 



EXERCISES 



ON THE CARBONIFEROUS GROUP. 



1. Name the authors and collections. ' ...' 



2. Mention the chief characteristics of the group. 



3. State the usual arrangement of the beds. 



4. Describe the chief coal-fields of England. 



5. Explain the origin of coal. 



6. Describe its deposition by subsidence, and state the 

 reasons for ascribing it to this agency, rather than to drift. 



7. Explain the nature of its vegetation. 



8. Describe the character of its climate. 



9. State any general phenomena, and pursue the accus- 

 tomed method of question and answer. 



