134 THE CANADIAN NATURALIST. [Vol. vii,. 



. The earliest known of these was the great vein of the Acadia;: 

 mine in the Cobequid mountains, discovered by the late Mr. G. 

 Duncan, and on which I reported in 1845. These hills consist 

 on their southern side of parallel bands of olive and black slate 

 with beds of quartzite, all very highly inclined. The iron vein 

 is a great irregular fissure, extending for many miles parallel to ^ 

 the bedding, and apparently accompanying a band of quartzite. 

 It contains in addition to crystalline and often micaceous Specu- 

 lar iron and Magnetic iron, large quantities of a rich earthy red; 

 ore, which from the crystalline planes which it presents, w^ould. 

 seem to have been a Carbonate of Iron decomposed and oxidised. 

 These iron ores are associated with large quantities of a crystal- 

 line ferruginous Dolomite, allied in composition to Ankerite. 

 This may be regarded as the veinstone to which the iron ores 

 are subordinate, and which in the thinner parts of the vein occu- 

 pies nearly its whole breadth. At the outcrop of the vein it is 

 in some places weathered to a great depth into a soft and very, 

 pure yellow ochre. Small quantities of sulphides of iron and 

 copper and of sulphate of barium are occasionally present. In 

 addition to the above, which may be regarded as the primary 

 contents of the vein, there occur in some parts of it secondary 

 deposits of concretionary Limonite, which have of late years- 

 afforded a very large part of the ore smelted by the Acadia. 

 Company. 



In some places the thickness of this vein has been found to 

 be 150 feet, with intercalated masses of rock, but it is very irregu- 

 lar, diminishing occasionally to mere strings of ankerite. It is 

 remarkable that in the Cobequid mount lins, which are cut by 

 transverse ravines to the depth of about 300 feet, the vein does- 

 not appear to be well developed in the bottom' of the ravines, but 

 only in the intervening heights At first I was disposed to ac- 

 count for this by supposing that the deposit is wedge-shaped, 

 diminishing dow^nward ; but I have more recently been inclined' 

 to believe that the large development of the vein is dependent on 

 differences in the containing rocks which have rendered them 

 harder and more resisting at the jDoints of such greater develop- 

 ments. 



With respect to the age of these beds, they must be older than 

 the Lower Helderberg rocks, which both at the eastern end of 

 the Cobequids and at the East River of Pictou, rest upon them> 

 They are on the other hand probably newer than the auriferous pri- 



