EXPLANATION OF JOGGINS SECTION. 201 



obliterate by passing downward immediately within the bark. The 

 calamites are rooted in shale, and the erect tree in an ordinary under- 

 clay, supporting a thin layer of coal which rises a little immediately 

 under the stump, being there either protected from pressure or increased 

 by the addition of woody matter derived from the trunk. This stump, 

 it will be observed, expands rapidly towards its base. This group 

 terminates upward in a mussel-bed resting on coal. 



The whole series of events in the preceding historical sketch has 

 depended on the following conditions : — Gradual and long-continued 

 subsidence, with occasional elevatory movements, going on in an exten- 

 sive alluvial tract teeming with vegetable life and receiving large 

 supplies of fine detrital matter. On the one hand, subsidence tended 

 to restore the original dominion of the waters. On the other hand, 

 elevation, silting up, and vegetable and animal growth built up succes- 

 sive surfaces of dry land. For a very long period these opposing 

 forces were alternately victorious, without effecting any very decided 

 or permanent conquest ; and it is very probable that the locality of 

 our section was, during this period, near the margin of the alluvial 

 tract in question, where the various changes of the conflict were more 

 sensibly felt and more easily recorded than nearer the open sea or 

 farther inland. 



The portion of the section above described in detail includes a 

 thickness of 2819 feet of the central part of the Coal formation, 

 constituting Division 4 of Logan's section. 



It is impossible to contemplate this vast series of deposits without 

 being forcibly impressed with the great lapse of time and variety of 

 change Avhich it indicates ; and a glance at the table of formations in 

 the introduction to this work, will show how small a portion of the 

 whole geological histoiy of the earth is represented by the coal 

 measures. It is to be borne in mind also that this section represents 

 the structure of the whole plain of Cumberland, and in a less precise 

 manner that of the whole Carboniferous areas of Nova Scotia and New 

 Brunswick, with great tracts composed of similar rocks, but not 

 elevated above the bed of the present seas. I do not wish it to be 

 understood, however, that all the changes represented by the Joggins 

 beds extended continuously over large areas. On the contrary, I 

 believe that had we visited Cumberland during the Coal period, we 

 might, by changing our position a few miles, have passed from a sandy 

 shore to a peaty swamp, or to the margin of an estuary or lagoon ; but 

 I believe that in each locality these changes .succeeded each other in 

 a similar manner, and that the great alternations between terrestrial 

 growth and marine deposition extended over very wide areas. Had 



o 



