'^8 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DoC. 20, 



Carboniferous. The Lower Coal-measures are, it is true, more 

 distinct in their flora from the Middle Coal-measures than the latter 

 from the Upper Coal-formation ; but still many species are common 

 to the two former, and the difference is small as compared with that 

 between the Lower Carboniferous and the Upper Devonian. The 

 Devonian rocks are also in this region unconformable to the Carbo- 

 niferous, having been disturbed and altered prior to the deposition of 

 the latter ; while no want of conformity, except of the local character 

 hereafter to be noticed, occurs in the Carboniferous. 



2. Physical Conditions attending the Deposition\of the Coal-forma- 

 tions. — The conditions of deposit implied in the mineral character of 

 the several formations above described, would appear to be of three 

 leading kinds : — (l)The deposition of coarse sediment in shallow water, 

 with local changes leading to the alternation of clay, sand, and 

 gravel. This predominates at the beginning of the period, recurs 

 after the deposition of the marine limestones in the formation of the 

 "Millstone -grit," and again prevails in the Upper Coal-formation. 

 (2) The growth of corals and shellfish in deep clear water, along 

 with the precipitation of crystalline limestone and gypsum. These 

 conditions occurred during the formation of the Lower Carboniferous 

 Limestone and its associated gypsum. (3) The deposition of fine sedi- 

 ment, and the accumulation of vegetable matter in beds of coal and 

 carbonaceous and bituminous shale, and of mixed vegetable and 

 animal matters in the beds of bituminous limestone and calcareo- 

 bituminous shale. These conditions were those of the Middle Coal- 

 formation. 



Within the limits of Wova Scotia, these conditions of deposition ap- 

 plied, not to a wide and uninterrupted space, but to an area limited 

 and traversed by bands of Silurian and Devonian rocks, already par- 

 tially metamorphosed and elevated above the sea, and along the 

 margins of which igneous action still continued, as evidenced by the 

 beds of trap intercalated in the Lower Carboniferous*; while about 

 the close of the Devonian period still more important injections and 

 intrusions of igneous matter had occurred, as shown by the granitic 

 dykes and masses which traverse the Devonian beds, but have not 

 penetrated the Carboniferous t- There is evidence, however, in the 

 Carboniferous rocks of the Magdalen Islands and of Newfoundland, 

 and in the fringes of such rocks on parts of the coast of Nova 

 Scotia J and New England, that the area in question was only a part 

 of a far more extensive region of Carboniferous deposition, the greater 

 part of which is still under the waters of the Atlantic and of the Gulf 

 of St. Lawrence. 



There is ample proof that most of the coarser matter of the Car- 

 boniferous rocks was derived from the neighbouring metamorphic 

 ridges ; but much of the finer material was probably drifted from 

 more distant sources. There seems no good reason to doubt that in 

 the Carboniferous period, and especially in those portions of it in 



* Dawson, Quart. Journ. Geol. Soc. vol. i. p. 329. 



t Dawson, Canadian Naturalist, 1860, p. 142. 



X Jukes's ' Newfoundland ;' • Acad. Geology,' p. 274. 



