NORTH SYDNEY AND SYDNEY MINES, C. B. — DeWOLFE. 321 



Coal seams. — True coal seams are small and few. One 

 often finds coal bands extending only a few feet, and not more 

 than an inch thick. Since they usually contain no underclay, 

 and are of limited lateral extent, they probably represent small 

 masses of leaves and driftwood buried quickly. When true 

 seams do occur, they possibly do not extend far, but have been 

 formed in small restricted shore swamps, much after the manner 

 of the thicker seams of the Coal Measures. The conglom- 

 erates contain more iron than t le surrounding grit. A 

 conglomerate layer, be it ever so small, usually exudes rusty 

 water. Th's is due partly to the cementing iron, but is to be 

 explained in part also by the fact that the more porous con- 

 glomerate acts as an underground drain by which the grit 

 continues to be further leached of its iron. 



The Ingraham coal seam is the only coal that has been 

 worked in the Grit. It must have been formed during a period 

 of tempoi-ary elevation of the bottom, or in a cove that had 

 been shut off from the sea. If it had formed during a period 

 of rest, when the land had risen merely by accumulation of 

 detrities, the intervening beach stage with its conglomerate 

 might be expected. This does not exist. The more probable 

 view, therefore, is that since this bed has not been traced far. 

 it is of small extent and formed in a large cove that had been 

 closed up by a bay bar. As the land sank, the bar grew in 

 height until a silting up of 25 feet of shale and underclay in 

 addition to two feet of coal had accumulated. Then the sea 

 again broke over the bar coverintr the whole area with coarse 

 sand which now almost approaches conglomerate. No part of 

 the bar, if such existed is now visible. 



From here to the top of the Grit series no important change 

 in the structure takes place. At Stubbart point, which has 

 been fixed upon as the boundary between the Grit and the Coal 

 Measures, alternations of sliale and sandstone again appear. 

 The oscillations which had marked the period of the Limestone 



