ANKERITE VEINS OF LONDONDERRY—LOUIS. 5d: 
the Ankerite veins, perhaps at the close of the Carboniferous 
epoch, the strata then existing were again much dislocated and 
fractured in consequence of further upheaval of the land in the 
Cobequid region, as is shown by the excessive faulting and 
numerous slickensides in the Ankerite veins. <A fresh series of 
fissures was formed in about the same line of weakness as before, 
but this time with an average direction of 10° S. of W. + Carbon- 
ated and erated waters, trickling through the Ankerite veins, dis- 
solved the Carbenates of Iren, Lime and Magnesia, perhaps with 
the simultaneous production of Red ore in the upper portions of 
the veins. The dissolved bicarbonate of Iron was then in its 
turn deeomposed, oxidised, and deposited in the form of a bog 
ere, together with some of the comminuted shales derived from 
the surrounding rocks, this being the source of the siliceous mat- 
ter present in the Londonderry Brown Heematites. These ores 
have all the appearance of bog ore, and also resemble it in com- 
position ; at times, too, they show small boulders of shale and 
Ankerite, as would be expected from such a mode of origin. 
They are thus secondary products of decomposition and solution, 
while the Red ore is the product of the primary decomposition 
in situ of the original Carbonates. 
The mode in which the Brown Hematites have been produced 
may be readily illustrated in the laboratory. In the course of 
some experiments on this subject, I found that when Ankerite 
finely ground was suspended in water, and a current of Carbonic 
anhydride passed through it for about 10 hours, 13.5 p.c. of the 
Ankerite was dissolved. On blowing air through the clear solu- 
tion, the Iron present was deposited in the form of ‘a yellowish 
brown hydrate. On repeating the experiment with Sidero- 
plesite, I obtained similar results, but the current of Carbonic 
anhydride was only kept up for about six hours, dissolving 8.2 
p.c. of the mineral. 
In conclusion, I once more wish to remind you that the geo- 
logical relations of these veins to the surrounding strata are yet 
very obscure, and that the sketch of their history which I have 
here attempted to produce, may at any time be liable to correc- 
tion when an exhaustive geological survey of the district shall 
have been made. 
