620 THE LOWER SILURIAN PERIOD. 



occupied by white fine-grained gneiss, with veins and masses of 

 granite, sometimes of a reddish colour. There is also much mica 

 slate, and dark-coloured clay slate, filled with crystals of the singular 

 mineral chiastolite or cross-stone. Near the extremity of Cape 

 Canseau specimens of this mineral occur, of a reddish or fawn colour, 

 three or four lines wide, and exhibiting the characteristic black cross 

 in considerable perfection. I have not found this mineral in any 

 other part of Nova Scotia. 



Having thus shortly surveyed this large though little explored 

 district, I may notice the probable arrangement of its beds, and the 

 causes of their present condition, the waste it has undergone, and the 

 materials it has contributed to newer formations, its useful minerals, 

 and the peculiarities of its surface and soils. 



The beds of the Lower Silurian district present a considerable uni- 

 formity of strike, in the direction already mentioned, along the whole 

 coast ; a fact which, in addition to the statements above made, is 

 curiously indicated by a table of compass dips and strikes of the 

 rocks on this coast now before me, and for which I am indebted to 

 H. Poole, Esq. In this table, out of eighty-three observations at 

 various places between Halifax and Yarmouth, the strike is between 

 W. and S. in seventy-three instances, and in a great many of these 

 not far from S. 45° W. The dips are, however, very variable, and 

 it is, in many cases, not easy to distinguish them from the slaty 

 structure, Avhich often gives planes much more distinct than those of 

 the bedding. On carefully examining a section, such as, for example, 

 that already referred to at Halifax Harbour and its vicinity, it will be 

 found that the beds undulate in synclinal and anticlinal curves, often 

 of no great magnitude, so that they are frequently repeated within a 

 few miles. This structure has been worked out in some detail by 

 Mr Campbell* in the country between Halifax and Windsor. In 

 other sections, however, as, for example, in that of the St Mary's 

 River, there appears to be an enormous thickness of beds with a 

 uniform dip. Reasoning on these facts, we arrive at the conclusion 

 that the alternations of quartz rock and clay slate constitute one 

 very thick formation having probably a predominance of quartzite 

 below and of slate above ; but whether the mica schist and gneiss 

 which occur on the peninsula of Cape Canseau, and also in Queen's 

 County and Shelburne, and the chloritic beds of Yarmouth, are to be 

 regarded as continuations of this series, differently changed by meta- 

 morphism, or as portions of other members of the Lower Silurian or 

 of still older deposits, remains uncertain. To settle this question, 

 * Report on Gold Mines of Nova Scotia. Journals of Assembly. 





