376 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
During the season of 1897 I visited a number of the most prom¬ 
ising portions of the series, with the intention of deciphering its 
history, as far as opportunity allowed. A review of certain points 
was possible during the following season. Much work has been 
done by local geologists in exploiting single areas; but, as far as 
the literature shows, no attempt has been made before to connect 
the bits of evidence which go to make up the story of the rocks. 
The region studied includes many of the exposures over an area 
roughly estimated at thirty miles square in the counties of Halifax 
and Colchester, and stratigraphically near the center of the series,, 
where the auriferous slates and veins are most prominent. Special 
attention was paid to Moose River Mines, Gay’s River Mines, Wav- 
erly, and Cow Bay. 
I am greatly indebted in the prosecution of the research to Prof. 
N. S. Shaler, and to the officers of the several mining companies in 
whose shafts and tunnels I worked. 
Structure and Characteristics of Portions of Halifax 
and Colchester Counties. 
Sediments. — Two main divisions of the series were early recog¬ 
nized by Campbell (’63). Of these only the lower, called by him 
the quartzite group, contains workable bedded veins. The latter 
are exposed intermittently in belts, especially east of Mount Uniake. 
The slates vary in texture, but their chief differences are due to 
secondary causes. The color is usually bluish; frequently, how¬ 
ever, altered to green by chlorite, to brown by the oxidation of 
pyrite, or to a gray by the loss of iron upon highly weathered sur¬ 
faces. Alternations of color in some places are frequent, while in 
others considerable masses may be uniform. This depends upon 
how thinly the rocks are bedded. Often, in the coarser sediments, 
leaves of schistose slate, only a fraction of an inch thick, will be 
found persistent for many feet. Again, it is a common condition 
for isolated sheets and lenses of slate to occur in the midst of a 
massive bed of sandstone. 
The arenaceous sediments include what the miners call “whin.” 
This term, originally used by Hutton in the sense of trap, and still 
employed in Cornwall with the same meaning, has been applied 
here to any kind of rock, other than slate, which cannot be mined. 
