WILLIAMS.] j. w. DAWSON. 289 



of the Albert mine, and yielding Lepidodendrons, Cyclopteris, and other 

 Carboniferous forms. The Carboniferous rocks, consisting of gray sand- 

 stones and shales, cover the central and eastern part of New Bruns- 

 wick. There is a slight nonconformity between the Lower Carbonifer- 

 ous and the Coal Measures of about 15°. They also appear in West- 

 moreland County, and extend along the north shore of the Bay of Fundy. 



Dawson 1 in 1806 gave an interesting discussion of the conditions of 

 deposition of coal, in which the classification and thickness of the Aca- 

 dian formations are stated. 



According to the estimates of Logan the Coal Measures at the Jog- 

 gins are 14,570 feet in thickness, the deposits of Pictou 16,000 feet, and 

 those of Cape Breton, according to Mr. Brown, 11,000 feet, excluding 

 the Lower Carboniferous deposits. 



The author arranged the Carboniferous series in the following groups: 



(a) Upper coal formation, consisting of sandstones, shales, conglomerates, and 

 thin limestones, bearing numerous plant remains. 



(&) The middle coal formation, or Coal Measures proper, containing all the coal 

 beds, but no limestones. Plant remains are quite abundant. 



(c) The " Millstone grit," including the saudstones and shales, lying just below the 

 Coal Measures. It contains the trunks of coniferous trees. 



(d) The Lower Carboniferous marine formation. 



(e) The Lower Carboniferous Coal Measures, or Lower Coal Measures. "The last 

 two groups are equivalent to the ' Subcarboniferous' of American geologists." But 

 the author did not find in Nova Scotia any reason for applying any more explicit 

 term than "Lower Carboniferous." 



There seem to have been three distinct conditions of deposition dur- 

 ing the middle coal formation: (1) Deposition of coarse sediments, 

 alternating with clays, sands, and gravels; (2) precipitation of lime- 

 stone and growth of corals and shellfish ; (3) deposition of fine sedi- 

 ments and accumulation of vegetable matter between bituminous 

 imestones aud shales. 



The condition of the Devonian rocks shows that there was considerable 

 igneous action at the close of the Devonian period, aud before the 

 deposition of Carboniferous rocks, from the fact that they are partially 

 metamorphosed by the effects of injection of igneous matter. 



The author thinks that the time of greatest depression was during the 

 deposition of limestones; the time of greatest elevation took place 

 during the formation of the coal beds, and the condition for the forma- 

 tion of the "Millstone grit" was intermediate. These remarks apply 

 to New Brunswick as well as to Nova Scotia. The local differences are of 

 the same character as those of the Appalachian and western fields and 

 those of Great Britain. 



There is marked evidence of a disturbance during the Carboniferous 

 period, producing synclinal and anticlinal fold&j similar to those of the 



•Dawson, J. W. : On the conditions of the deposition of coal, more especially as illustrated hy the 

 coal formation of Nova Scotia and New Brunswick. Quart. Jour. Oeol. Soc, vol. 22, 1866, pp. 95-166, 

 plate. 



