386 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
cent slates, very rarely and only to a slight extent by other members 
of the series. They are found sparingly on the sides of the east- 
west anticlines, but are common where the axes of these are made 
to plunge downward by the doming effect of the north-south fold^ 
ing. In a few instances they may be horizontal; but usually they 
have a distinct pitch dependent upon the degree of inclination of 
the axes of the folds, the thickness of the leads, and the character 
of the country-rock. In this they are not exactly coincident with 
the bedding, for On a plunging axis they converge at smaller angles 
than those of the strike lines. 
A noticeable feature is the local nature of the distortions. Near 
the vein the stratification of the slate follows closely the twisting of 
the quartz. As one recedes from it, however, the bedding-planes 
become less strongly crenulated, until from an inch to several feet 
away the waves die out. The coarser the sediment, the less it has 
yielded visibly to the forces ; and in contact veins the quartzite 
wall is even, and the slate wall rolled more than is usual in veins 
which lie wholly within the slate, at some distance from any whin. 
The appearance suggests that there may be a compensation, the 
rigidity of the whin forcing greater buckling in the more plastic 
slates. In still other cases, where the vein is in slate, but within a 
few inches of a quartzite bed, the slate on the side toward the whin 
is crenulated and crushed till the particles have little power of 
coherence ; and on the other side the rolling is regular and the 
slate bent without fracture. In general, however, the corrugation 
has weakened the sediments near it. 
A structure similar to rolling is observable in sections of the 
Cretaceous clays and sands of the Atlantic coastal plain. In these 
water, often bearing iron, has buckled up the clay laminae in a 
manner precisely similar, leaving adjacent sands untouched. The 
phenomenon has no necessary relation to the concentration of gold, 
although barrel quartz is considered by many Nova Scotian miners 
as sure to be rich; but in some veins it appears that gold was either 
brought up by the new solutions, or concentrated from the sedi¬ 
ments at about the time of corrugation, and now lies on the borders 
of these rolls in pockets. 
In Moose River rolling can be studied in detail, although the 
lack of coincidence between the attitude of the rolls and that of 
the axes of the main folds is not very marked. The best places 
for observation are quarries near the road, and winding tunnels 
