1853,] DAWSON COAL-MEASURES, NOVA SCOTIA. 17 



however, eventually became an undersoil, and a thin coaly layer 

 accumulated upon it, to be buried under a thick bed of clay. These 

 changes appear to require movements of elevation as well as of subsi- 

 dence. It is possible, however, that the appearances in this particular 

 group may be due to the heaping up and subsequent rupture of a 

 beach or bar at the margin of a morass. 



In the next group we have another thick series of sands and clays, 

 with only one terrestrial surface, now an arenaceous underclay, with 

 Stigmaria-rootlets, and an erect ribbed stump, 2 feet high by 1 foot in 

 diameter. In the lowest sandstone are many drifted trees, indicating 

 that there was neighbouring forest-land undergoing denudation. 



Group VII. presents the usual succession of underclay, coal, and 

 Modiola-limestone and shale. The latter is remarkable for its great 

 thickness, indicating the lapse of a very considerable time without any 

 inroads of mechanical detritus. The succeeding group, however, filled 

 up these quiet waters with a great mass of sand and clay. 



Group IX. is a fine series of underclays and coals, alternating with 

 Modiola-beds. It contains nine distinct soil- surfaces, the highest 

 supporting an erect tree, which appears as a ribbed sandstone cast, 

 5 feet 6 inches high, 9 inches in diameter at the top, and 15 at the 

 base, where the roots began to separate. This tree being harder than 

 the enclosing beds, at the time of my visit, stood out boldly at the 

 base of the cliff, nearly three-fourths of its diameter, and the bases of 

 three of its four main roots, being exposed. Five of the underclays 

 support coals, and in three instances bituminous limestones have been 

 converted into soils, none of which, however, support coals. The 

 last of these bituminous limestones is a very remarkable bed. First 

 we have an underclay; this was submerged, and a Sjnrorbis, or crea- 

 ture allied to this genus, which we shall find to be very common in 

 the succeeding parts of the section, attached its little shell to the 

 decaying trunks, which finally fell prostrate, and formed a carbona- 

 ceous bottom, over which multitudes of little crustaceans (Cypris) 

 swam and crept, and on which 14 inches of calcareous and carbona- 

 ceous matter were gradually collected. Then this bed of organic 

 matter was elevated into a soil, and large trees, with Stigmaria-roots, 

 grew on its surface. These were buried under thick beds of clay and 

 sand, and it is in the latter that the erect tree already mentioned 

 occurs ; its roots, however, are about 9 feet above the surface of the 

 limestone, and belong to a later and higher terrestrial surface, which 

 cannot, however, be distinguished from the clay of similar character 

 above and below. 



The Xth Group contains a vast thickness of sandstones and shales, 

 the latter chiefly of chocolate colours, which, as they afforded few 

 facts of interest, were not measured in detail. This group points to 

 a long-continued interruption of the swamp-deposits previously in 

 progress. During the greater part of the time occupied in the forma- 

 tion of these beds, the locality must have been a sandy or muddy sea- 

 bottom, receiving much mechanical detritus, or an expanse of flats 

 of reddish mud and brown or grey sand, covered by the tides. There 

 are, however, some evidences of terrestrial conditions. In the lowest 



VOL.. X. PART I. C 



