318 THE CARBONIFEROUS SYSTEM. 



of Sir W. Logan's Joggins section. These occupy the East Branch and 

 Main River for some distance. They contain a few fossil plants, in 

 one instance impregnated with carbonate and sulphuret of copper; 

 and at least two beds of limestone, not rich in fossils, but affording the 

 characteristic species Terehratula sacculus, Streptorhyncus crenistria, 

 and Productus semireticulatus. One of these limestones, seen near 

 the forks of the river, is remarkable for showing, when slices are 

 examined under the microscope, that it is made up of small fragments 

 of shells with entire specimens of very minute species.* The rocks 

 in this part of the section are much fractured ; but a comparison with 

 the continuation of the same beds in M'Lellan's Brook, shows that the 

 order is ascending, and that the Coal measures rest on the rocks last 

 described. 



The Coal measures of the Albion Mines consist of the same materials, 

 and contain many of the same fossil remains with those of the Joggins ; 

 but they differ in the arrangement of these materials and fossils. 

 Instead of a great number of thin beds of coal and bituminous shale, 

 we have here a few beds of enormous thickness, as if the coal-forming 

 processes, so often interrupted at the Joggins, had here been allowed 

 to go on for very long periods without interference. It is almost a 

 necessary consequence of this that erect plants are not found in the 

 Albion measures, and that well-preserved vegetable fossils are com- 

 paratively rare, while vast quantities of vegetable matter have been 

 accumulated in the state of coal. The sections at the Albion Mines 

 are not perfect. They show, however, five or six seams of coal, and 

 an immense thickness, perhaps 800 feet, of black shales with Cypris 

 and remains of ferns and other leaves. There are also underclays and 

 ironstones abounding in Stigmaria. 



In attempting to give a general idea of the structure of this coal- 

 field, I shall first notice the order and succession of the beds, then 

 their distribution, and next some remarkable and exceptional features 

 which they present, as compared with the districts previously noticed. 



The section of the beds, in descending order, as made up fi'om a 



comparison of the results of borings and excavations by the different 



coal companies, is as follows : — 



Ft. in. 



Gray freestone or sandstone . . . . . 15 3 



Black shale and clay, with layers of dark argillaceous 



sandstone and ironstone ■]- . • . . . 419 9 



Forward, 435 



* See Table in last chapter. 



t These beds are given from the observations of Mr Hudson in the Forster Pit, 

 Albion Mines. 



