510 THE DEVONIAN PERIOD. 



of these rocks bends slowly around, assumes a southerly direction, 

 and follows the last named stream to within a few miles of its mouth. 

 Again changing its direction, it now flanks the end of the Bloomsbury 

 ridge, and extends in a narrow belt eastwardly as far as the east branch 

 of the Black Kiver. Beyond the latter, as far as known, it rapidly 

 disappears. 



" To the west of St John, besides the locality of Manawagonish, the 

 Dadoxylon sandstones have been observed on the west branch of 

 the Musquash River, in the village of Ivanhoe, resting upon a deposit 

 of the Upper Bloomsbury and overlaid by Cordaite shales. 



" It will be remarked, when describing the characters of the Blooms- 

 bury group, that the red deposits, which form its upper member, 

 constitute beds of transition between that group and the one now 

 under consideration. 



" As indicated by the name it bears, the Dadoxylon sandstone is 

 chiefly composed of coarse materials, though less so than in the group 

 which immediately preceded it. While the upper beds of the latter 

 consisted chiefly of reddish conglomerates, the present series is com- 

 posed of a hard gray sandstone, associated, however, with occasional 

 beds of grit and layers of dark gray shale. The transition above 

 alluded to consists, therefore, in a gradually increasing fineness in 

 the sedimentary beds, indicating changes in the physical conditions 

 under which they were deposited. 



" In lithological characters, the Dadoxylon sandstone, as described 

 by Mr Matthew, is remarkably imiform and constant, and has been of 

 great service in the study of the geology of the section now under 

 consideration. But the chief interest which attaches to this deposit, 

 is derived from the abundance and wonderful perfection of the organic 

 relics which it holds, the oldest undoubted relics of a land vegetation 

 in this long series of formations." 



Bloomsbury Group. 



The Bloomsbury group, like the Coldbrook, which it closely 

 resembles, comprises two very different series of sediments, the 

 lower and older being volcanic, while the upper and newer is of 

 aqueous oi-igin. These must be separately considered. 



" (A.) Sedimentary Beds. — The deposits of the Upper Bloomsbury, 

 of purely aqueous origin, are generally found in bands of varying 

 width, lying parallel to, and immediately above the volcanic deposits 

 of the lower member. They may thus be traced, following the 

 different distribution of the latter, almost throughout its entire extent. 

 The greatest development of this member is along the space between 



