80 TRANSACTIONS OF THE [Nov. 20, 
GENERAL GEOLOGICAL RELATIONS. 
In both Stirling Hill and Mine Hill, the ores form a bed 
which is in each case, so far as one can see, parallel to the bed- 
ding of the containing limestone. The limestone is coarsely 
erystalline and is white. It outcrops as a continuous belt of 
varying width and somewhat over 30 miles in length. At Og- 
densbureh, which is near its southern end it is a half mile wide, 
and at Franklin rather less. In the area with which we are 
concerned the white limestone rests on the west against the 
oneiss, which forms the Pimple Hills and which is parallel with 
the white limestone in strike and dip. Nevertheless the strike 
and dip of the latter are often obscure, on account of its massive 
habit. The white limestone is closely involved throughout all 
of its extent with a blue variety, which is of Cambrian or Cam- 
bro-Silurian age. It has been a much argued question for many 
years as to whether the white is altered blue or is a member of 
the gneiss series and therefore Archean. A full historical re- 
view of this question is given by F. L. Nason in the American 
Geologist, VII. 241, April, 1891, and an important contribution 
in the New Jersey Report for 1890. The point at issue is 
briefly this: The white limestone is pierced in countless places 
by granitic dikes, which now appear in more or less detached 
masses, apparently stretched out thus by foldings and disturb- 
ances. More basic varieties, seeming to be altered gabbros, are 
also recorded by Nason, and some extremely interesting trap 
dikes. The white limestone, it may be added, is also charged 
with curious bunches of silicates, especially near the mines, 
which, if they are originally igneous rock, are now much meta- 
morphosed. They contain well crystallized orthoclase, biotite, 
pyroxene, hornblende, garnet, etc. It is a very important point 
that the white limestone is penetrated by the intrusions noted 
above, and much stress will be laid on it later. 
The terms bed and vein are used somewhat interchangeably 
in the subsequent description. Locally the ore body is always 
spoken of as a vein, and the parts are called the front vein, the 
back vein, ete. But as the ore is parallel to the bedding it may 
also be called a bed, and is so by Credner. In using this latter 
term, which I prefer, I would not mean thereby that the ore is 
necessarily older than the hanging and later than the foot, and 
thus deposited in the regular ‘sedimentary series, although this 
definition of bed is insisted on by many writers. It is “merely 
intended to convey the idea that the ore is interbedded. 
THE OGDENSBURGH ORE Bopy. 
As shown on the map, which is reproduced from a topographi- 
