NORTH SYDNEY AND SYDNEY MINES, C. B. DeWOLFE. 817 



between the two places. But it is not hard to believe that such 

 diversity could occur in tiiat distance, for a difference of some 

 inches in coal and of some feet in strata is often seen in the part 

 exposed in one cliff. Moreover, the Indian Cove seam, for 

 example, where it is now worked near the outcrop, is four feet 

 thick ; while in some other places it has been cut through in 

 two feet. The Main seam presents undulative and varying 

 thickness as it is worked at different points. With these facts 

 in view, it is (|uite probable that the Black Point and Chapel 

 Point seams are the same. 



Part II. Summary of History. 



The rocks included in the area under discussion are all 

 sedimentary. Nearly all give evidence of deposition in shallow 

 water. This could happen tliroughont such great depth only 

 in the case of a slowino- sinking; land. There are a few indi- 

 cations of more rajjid or svidden sinking, but rocks formed 

 under suddenly changed conditions are a very small part of the 

 whole deposit. 



LIME'.STONE SERIE.«5. 



Limestones. — The total thickness of strata from Leitch's 

 creek to Cranberry Head is about (j400 feet. The lower beds 

 at Leitch's creek are a laminated calcareous sandstone resting 

 upon limestone. Tiie presence of limestone containing marine 

 fossils is proof of formation under the water of the open sea. 

 After this condition had remained for some time the waters, which 

 must have been shallow, became partly flooded with sand. 

 Its deposition was probably slow, thus allowing it to be so thor- 

 oughly impregnated with lime. Since this sand now forms a 

 bed nearly 200 feet thick, gradual depression must have taken 

 place for a long time. At last some change in the supply of 

 detritus brought clay instead of sand, now forming a bed of 

 red shale two feet thick. This is succeeded by limestone which 

 could have come from two sources. Either it could have been 

 carried from some land reef of limestone by water containing 



