266 THE CARBONIFEROUS SYSTEM. 



Crossing Cobequid Bay from the moutli of the Folly to that of the 

 Shubenacadie, we find the first rock that appears at the mouth of the 

 latter to be a black laminated crystalline limestone without fossils, and 

 supporting a great thickness of marls and gypsum similar to those of 

 Windsor. I spent several days in exploring this section in 1842, in 

 company with Sir Charles Lyell, and the late Mr George Duncan of 

 Truro. The limestone and marls resting on it dip to the south-west. 

 It thus appears that the Lower Carboniferous beds on the opposite 

 sides of the bay dip inland, so that the bay forms, in so far as these 

 I'ocks are concerned, an anticlinal valley — a somewhat rare occurrence 

 in this region, where the beds of sedimentary rocks usually dip away 

 from hills rather than from depressions. The rocks in the banks of 

 the Shubenacadie are, however, much broken by faults, though the 

 general dip in the lower part of the river appears to be to the south- 

 ward. The rocks succeeding the " Black Rock " limestone, for about 

 three miles up the estuary of the Shubenacadie, consist principally of 

 soft marly sandstones filled with veins of reddish fibrous gypsum, 

 which run in every direction, and form a network so complicated that 

 it is difficult to understand how the rocks could have been supported 

 in such a manner as to leave open the fissures which the gypsum fills. 

 It is possible, however, that these cracks were not all open at once, 

 but were produced by different movements to which the mass has 

 been subjected; and there is another way of accounting for this 

 appearance, to be stated shortly. There are also a few wide veins 

 filled with the peroxide of iron and sulphate of barytes. The former 

 is in part in the red ochrey state, and in part in the state of red and 

 brown hematite, often in beautiful coi'alloidal forms with an internal 

 fibrous structure. The barytes is in small tabular crystals. These 

 veins also contain oxide of manganese and calc-spar. Their contents 

 were probably introduced by water, rising from rocks beneath which 

 afforded these materials.* 



The reader will observe that the venis of gypsum contained in these 

 rocks are very distinct from the large beds of the same mineral. The 

 latter were formed as horizontal layers at the same time with the 

 containing beds. The former have filled up cracks opened after the 

 beds were consolidated. The fibrous texture, which the gypsum veins 

 nearly always display, arises from the circumstance that little slender 

 prisms of the mineral have sprouted forth from the sides of the fissures 

 until they filled them. Hence they always stand at right angles to 

 the sides of the vein. Similar appearances are observed in the greater 



* For the manner in which these minerals may have been formed, see descriptions 

 of mineral veins at Five Islands and Acadia Mine. 



