WOODMAN: GOLD-BEARING SLATES OF NOVA SCOTIA. 397 
folds plunge. They were made by a revival of vein activity. Either 
some concentration of gold took place at the same time, as shown 
by certain pockets on the sides of rolls, or else all or part of this 
gold was brought up by the new solutions. 
As regards origin, held evidence leads directly to the theory that 
rolling was caused in part by the north-south folding, in part by the 
slow entrance, subsequent to the formation of the veins, of more 
silica than could be accommodated readily in the space. The 
orogenic forces had created weakness. The new silica made its 
way along these planes, where pressure was relieved by parting of 
the strata. Not being satisfied with the space already provided, it 
buckled up the strata nearest it, whenever the surrounding sedi¬ 
ments were not too unyielding, until the pressures were equalized 
and no more material could enter. Faulting, closing the second 
epoch of orogenic action. These dislocations ran in the direction 
of the newer folds, and cut off the rolls. In some instances simple 
joints were formed, without lateral movement. Where the second 
period of disturbance has not faulted the rocks, it appears in some 
regions to have jointed them north and south, and a few of the 
fissures are filled with veins. Other systems appeared probably 
at various times, and the history of each district must be studied 
separately. Very little mineralization took place after these last 
planes of separation were formed. In some places joints have 
curved in passing rolls, as cleavage has done. 
Local revival of vein action, marked in such places as Cow Bay. 
The gold in the veins there probably entered from below with the 
gangue. 
Cleavage, striking about N. 60° E., and cutting all the veins. 
The effect was produced by pressure apparently nearly parallel to 
that which gave the first folding. The conditions of the sediments 
were different, however, at this later epoch. Instead of the plas¬ 
ticity due to youth, lack of complete consolidation, and a consider¬ 
able load of superincumbent rock, the force had to deal with 
rigidity, rendered greater by the quartz veins scattered through the 
mass, and probably with a much reduced load, which would of 
itself decrease plasticity. 
After these occurred certain other details of the history, to which 
no definite order is assignable. An irregular local faulting is one 
of the latest in many {daces, and may be due to comparatively 
recent warping from some of the last oscillations of the peninsula. 
