398 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
This or some other orogenic movement of wide extent and slight 
effect has inclined the cleavage at most points. As it has not 
altered the strike of the planes of fissility, it acted parallel to the 
force which produced these planes. A small concentration of 
sulphides may have taken place also since the cleavage (Hamilton, 
’66); but the presence of sulphides in the planes maybe due, on 
the other hand, to the stretching and shearing of crystals which lay 
in the bedding. These occurrences often accompany bright slick- 
ensides. Veins 'of various ages fill irregular fissures, and are 
generally barren. I have not found any penetrating into the lower 
Carboniferous rocks, and believe that thev are all older than this 
t / 
period but younger than the cleavage and most of the jointing. 
How many cycles of erosion the series has suffered cannot be 
determined. At Gay’s River Mines all the features noted elsewhere 
can be seen in the rocks underlying the lower Carboniferous con¬ 
glomerate, but stop at its base. The latter has suffered no distur¬ 
bance sufficient to fold or fault it, although slickensides on the 
pebbles and cement tell of internal movement. It is highly proba¬ 
ble, therefore, that all of the effects outlined above had been com¬ 
pleted long before that time, for the boulders in the conglomerate, 
largely from the slate and whin and veins, exhibit the same phenom¬ 
ena as the underlying rocks. The structure of the older sedi¬ 
ments, and the character of their contact with the conglomerate 
above, show that the former series Avas denuded before Carbonifer¬ 
ous times, probably the larger part of the original mass having 
been lost. The history since the Carboniferous is in great measure 
problematical, but what we know of the structure indicates that 
the topographic changes have been far less than those which took 
place before. 
Summary of Early Studies. 
The metamorphic series early attracted the attention of obseiwers, 
but the main activity shown in its study Avas manifested imme¬ 
diately after the discovery of gold about 1860. On the AAdiole, the 
work done upon the rocks has been unsystematic, with the excep¬ 
tion of that carried on by the Geological survey of Canada. The 
following notes are arranged chronologically, to give the advance 
in knowledge of the whole series rather than of particular prob¬ 
lems connected with it. 
