396 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
true uniformly of the pyrite, and to a great extent of the arsenopyrite* 
In some places chalcopyrite appears in cleavage planes, in thin 
sheets with bright surfaces. In such cases it is still a question 
whether it was deposited there, or whether it has been drawn out 
by subsequent displacement. The gold was concentrated at the 
same time with the sulphides. The gathering took place under the 
influence of solutions percolating laterally and still more downward,, 
as shown by the attitude of much of the ore. This movement has 
continued in a very small way ever since its beginning. The faults 
of the two periods of disturbance are rarely filled with ore, and 
where they are its origin is not clear. Regional metamorphism of 
the series, manifesting itself in yet other ways, belongs to the same 
period. The chlorite is chiefly in bedding-planes, as far as studied 
but much remains to be learned. The same may be said of the 
secondary muscovite and calcite. 
Granites may have come in between this and the next event, but 
probably not until after both periods of orogenic disturbance and 
before the cleavage. They are said to intrude between bedding 
planes in some places, and to have no perceptible influence upon 
the distribution of the veins, or of the gold in them or in the sedi¬ 
ments ; but few data are available. The granite at Halifax appears 
not to run into bedding-planes, nor do these planes seem to buckle 
up over the intrusive mass. One thing must be remembered, how¬ 
ever, in any attempt to classify the intrusives of granite in a time- 
scale of the history of the series. We have no proof whatever that 
the areas of granite are all of the same age, and for the present the 
evidence presented by each batholitic mass must be examined 
separately. 
First period of folding, giving east and west folds, with few 
faults, flexing veins and bedding-planes alike. The coarser grits 
were corrugated with as much ease as the finest pelites, as though 
the mass were quite plastic. This condition obtained from the low¬ 
est to the highest member of the series as we have it now, showing 
that vastly more of it existed then. 
Second period of folding, extending forward for a considerable 
time and forming waves whose axes run roughly north and south. 
The action loosened the strata somewhat, giving opportunity for 
the following consequences. 
Rolling of portions of the veins and adjacent beds, at points on 
the sides of the second series of folds where the axes of the first 
