1850.] DAWSON METAMORPHIC ROCKS OF NOVA SCOTIA. 361 



the ochrey red ore. The irregularity of its distribution would result 

 from that of the carbonate of iron, which, where it now occurs in 

 the vein, is seen to be confusedly mixed with the ankerite. It might 

 also happen that the heat would act most powerfully along lines of 

 fissure, and of this there are some evidences in the appearance of the 

 vein. The comparatively unaltered state of the ankerite is explained 

 by the fact, that it is less easily decomposed by heat than the pure 

 carbonate of iron, or even than the spathose iron found at Acadia 

 Mine. If a small fragment of the mixed white ankerite and spathose 

 iron from Acadia Mine be exposed to a low red heat with access of air, 

 the carbonate of iron is completely decomposed, before any other 

 change than a slight discoloration is produced in the ankerite. 

 Hand specimens from the Acadia Mine often present appearances 

 highly illustrative of the relations of the red ore to the other ingre- 

 dients of the vein, and confirmatory of the above views of its origin. 

 Fig. 4 is a sketch of one surface of a specimen of this kind. 



Fig. 4. — Surface of a Hand-Specimen from Acadia Mine. 



a. Ankerite. 



b. Spathose iron. 



c. Red iron ore. 



d. Fragment of slate. 



e. Ankerite with surface changed into yellow ochre. 

 /. Fissure lined with red ore. 



The brown hcematite is apparently confined to the superficial parts 

 of the vein; and indeed appears to have been more abundant in 

 those parts of it which have been removed by denudation, than in 

 any now remaining. It is no doubt a product of the action of water 

 on the carbonate and hydrated oxide of iron, near the outcrop of 

 the vein. 



The sulphate of barytes, occurring in small quantities in some 

 parts of the vein, must also be a product of aqueous infiltration. 



The facts which I have obtained in relation to the age of this de- 



