1853.] DAWSON COAL-MEASURES, NOVA SCOTIA. 13 



stances of phsenomena seen also, but less distinctly, in other parts of 

 the section. Fig. 1 exhibits apparently the edge of a channel, cut 

 in clay, and filled with sand and drift-trees, just as tidal and river 

 channels in estuaries are now often filled with the debris borne down 

 by an inundation or thrown in by a storm. 



On the whole we may conclude that the sandstones mark tem- 

 porary, and often very local, interruptions of the quiet deposition of 

 clay and organic matters, which occupied the greater part of the 

 time in which the beds of this section were formed ; but that these 

 interruptions were not of such a character as to transport coarse 

 detritus, or such as occurred in a locality very distant from rocky 

 promontories or gravel beaches. 



3. Of fifty-four beds of Coal noted in the section, only three or 

 four are sufficiently large to be worked with profit. That at 

 present mined is 3^ feet in thickness, and the underlying bed 1 8 inches 

 thick is worked with it, making in all 5 feet of coal. The coal of all 

 the beds is of a free-burning bituminous quality, somewhat resembling 

 that of Sydney, Cape Breton, though generally inferior in point of 

 purity. The beds of coal are much more uniform in their thickness 

 than those of sandstone and shale. Fig. 3 ms. shows an instance in 

 which the clay-parting between two thin beds varies in thickness ; 

 and the clay between the two seams of the main-coal is said to thin 

 out in working to the eastward. 



In a section so perfect as that of the Joggins, excellent oppor- 

 tunities are afforded for inquiring into the circumstances under which 

 beds of coal were accumulated, and some of the smaller and more 

 shaly beds are more instructive in this respect than those of greater 

 magnitude and purity. As has already been pointed out by Mr. 

 Logan, the most constant condition required for the growth of coal 

 is the occurrence of a bed of clay or argillaceous sand with Stigmaria ; 

 in other words, a soil with roots of trees of the tribe most abundant 

 in the swamps and alluvial flats of the period. In most of these 

 " underclays" only the straight cylindrical " rootlets," peculiar to 

 Stigmaria, were observed ; but in several instances the roots with the 

 rootlets attached, and even stools with roots radiating from them, 

 were observed. Only three instances are noted in the section of 

 coals without perceptible Stigmaria-roo\\ti^ in their underclays. In 

 one of these cases there were thin fibrous roots, and in two the 

 coaly layers supported by the clays were almost entirely composed 

 of leaves of Poacites. Some of the underclays are fine and argil- 

 laceous, and where recent must have constituted soft mud, or stiff 

 retentive clay. The greater number are, however, argillo-arenaceous, 

 and some decidedly sandy ; and it is observable that many of the 

 more argillaceous underclays are thin, and rest on beds of sand, into 

 which the roots and rootlets often descend. In the section there are 

 sixteen underclays more or less argillaceous and having a thickness 

 exceeding 2 feet, without the intervention of sandstone. There are, 

 however, eighteen of 2 feet or less in thickness, and resting on 

 sandstone, coal, or bituminous limestone. Two only are decidedly 

 sandy, although there are a number of arenaceous underclays 



