1853.] 



DAWSON — COAL-MEASURES, NOVA SCOTIA. 



29 



above the erect plants, that the rootlets of one underclay pass downward 

 among the erect Calamites, and the rootlets of another pass beside 



Fig. 8. — Section from the lower part q/" Group XXVII. (p. 3). 



1, Shale. 2. Shaly coal : 1 foot. 3. Underclay with rootlets : 1ft. 2 in, 



4. Grey sandstone passing downwards into shale : 3 ft. Erect tree with Stigmaria roots (e), 



on the coal. 



5. Coal: 1 inch. 6. Underclay with roots : 10 inches. 



7. Grey sandstone : 1 ft. 5 in. Stigmaria rootlets continued from the bed above ; erect Cala- 

 mites. 8. Grey shale, with pyrites. Flattened plants. 



and within the cast of the erect tree, and have helped to obliterate 

 its surface-markings, by passing downward immediately within the 

 bark. The roots of this tree are casts in sandstone, probably from 

 the surface of the sand surrounding its upper part, but the stump 

 itself is filled with shaly clay from the underclay above. It will 

 be observed that one of the bituminous limestones in this group 

 has been converted into a Stigmaria-underclay and supports an 

 erect tree. 



In Group XXVIII. and the remainder of the section, we find 

 gradually decreasing evidences of group conditions ; and in other 

 beds higher than those in our section, there are conglomerates and 

 other evidence of very different conditions from those we have been 

 considering — in short, of a return to the open sea of the Lower 

 Carboniferous period. In Groups XXVIII. and XXIX., however, we 

 have still a number of underclays with thin coal seams and erect 

 plants ; among the latter some large ribbed trees and two stumps 

 converted into coaly matter, and with irregular coaly roots. 



In conclusion, it appears evident that the series of events indicated 

 by this remarkable section, and which I have endeavoured to state in 

 the above historical sketch, consists of a long succession of oscillations 

 between terrestrial and aquatic circumstances, and unaccompanied by 

 any material permanent change in the nature of the surface or in its 



