1853.] DAWSON — COAL-MEASURES, NOVA SCOTIA. 1.5 



True drift phsenomeua are confined to the presence of trunks of trees, 

 sometimes carbonized, in the sandstones, and of fragments of mineral 

 charcoal, the scattered debris of decayed trees, on the planes of 

 lamination of the coal. 



4. The Bituminous Limestones are beds of animal origin, being 

 composed of the remains of shells of Modiola and Cypris, with 

 coprolites and other remains of Fishes, the whole blackened by 

 coaly matter. They are now hard and sonorous, though the pene- 

 tration of some of them by Stiffmaria-xoots and rootlets shows that 

 they were once soft and marly. They generally pass upwards into 

 Modiola-shales, which are, in truth, their upper portions less de- 

 com]josed at the time of their burial, and somewhat more mixed with 

 argillaceous matter. These beds mark the slow and long-continued 

 accumulation of animal matter in clear water, probably brackish. 



It is remarkable that in almost every instance the conditions re- 

 quisite for the formation of these limestones and their allied Modiola- 

 shales have followed immediately on the formation of layers of coal 

 based on underclays= This association with coal also occurs in several 

 instances in the Sydney Coal-field *, and the two principal seams at 

 Pictou have beds with remains of Fishes and Cypris in their roofs. 

 At Sydney and Pictou, however, this appears to be the exception 

 instead of the rule. 



III. Historical Sketch of the sequence of events indicated by the 



Section. 



The section at the Joggins is so perfect, and speaks so plainly of 

 the mode of formation of its beds, that it does not seem to me pre- 

 sumptuous to attempt to read it as a connected history. In doing 

 so, I of course follow the ascending order, and have therefore, in the 

 sectional list (pp. 2 et seq.), numbered the groups of beds from the 

 bottom toward the top. The subdivision into groups is merely to 

 facilitate reference ; and in so far as it is natural, is based on the fact 

 that the section presents, in some places, a succession of beds crowded 

 with interesting evidences of vegetable and animal life, and in others 

 thick groups of strata comparatively barren in these respects. 



At the base of Group I. we find an underclay, or fossil soil of 

 argillaceous character, and 4 feet in depth, penetrated by rootlets 

 oi Stigmai'ia. Below this soil there are sandstones and shales having 

 a few drifted trunks of trees imbedded in them ; above it is a series 

 of beds marking very tranquil and slow accumulation of organic and 

 fine sedimentary matter. The published observations of Mr. Binney, 

 Mr. Brown, and the writer f, as well as facts to be subsequently 

 noticed in this paper, amply prove that the StiymaricB were roots of 

 the Sigillaria and its allies. We therefore take it for granted that a 

 forest of Sigillarice grew on this soil, the remains of which and of 

 the vegetable soil which accumulated around them have produced 

 half an inch of coal. The cause of the disappearance of the forest is 

 revealed by the next succeeding bed, a bituminous limestone with 



* Mr. Brown's Section, Quart. Journ. Geo). Soc. vol. vi. p. 116. 

 t Quart. Journ. Geol. Soc. vol. ii. pp. 134, 390, 393, &c. 



