90 TRANSACTIONS OF THE [Nov. 20, 
dicate, with a fairly close approximation to scale, the vertical 
extent of the collapsed anticline, and the depth along each sec- 
tion, at which the front vein may be expected to fold upward 
into the back. It will be interesting to see if future mining 
establishes these inferences, and if when the indicated bottom 
of the back vein or collapsed anticline is reached the ore ends, 
or whether it separates into two beds (the flanks of the anticline), 
one joining the front vein, and the other dipping off downward 
or eastward from it. 
ON THE ORIGIN OF THE ORE. 
Having the structural features before us, we may discuss the 
probable form of origin. This is a puzzling problem, the more 
because the minerals so abundant here, franklinite, zincite and 
willemite, are either unknown or extremely rare elsewhere in the 
world. Evidently the general method of origin for the ore- 
bodies of both Stirling Hill and Mine Hillis the same. I do 
not think they were ever continuous because they appear at 
different horizons in the limestone, with reference to the gneiss. 
In throwing what light we can on the origin, it is important to 
note— 
1. That of the ores franklinite is much the most abundant 
mineral, and that this contains much more iron than anything 
else. Mr. Stone’s four analyses (cited at outset), show from 
56.57 to 67.38 per cent. Fe,O,. Mr. Van Dyck (N. J. Rep. for 
1868. p. 673) found 74.8 Fe.0.. The deposit is essentially one 
of iron oxide, with extraordinary amounts of manganese and 
zine. The same chemists found from 7.8 to over 15 per cent. 
oxide of manganese, and from 15.91 to over 21 per cent. oxide 
of zinc. Oxides of manganese are frequent associates of iron 
ores, and zinc blende is also known, but always as an unimport- 
ant mineral.* In distinctively zinc mines iron oxides are wide- 
spread, although manganese is a rarity. 
2. That it is a remarkable and exceptional thing not to find 
more lead with so much zine, for where zine is found in lime- 
stone as it usually is, we almost always meet lead and con- 
versely. Although galena is found in these mines, it is a rare 
and insignificant mineral. 
3. From experience with oxidized ore bodies of zine and iron 
(manganese as stated is unusual) elsewhere (Southwest Virginia, 
Belgium, Raibl in Karinthia, Silesia, Laurium in Greece) the 
*Zine oxide has been caught at the tunnel head of furnaces smeltiug Vir- 
ginia limounites. -E. C. Means, ‘‘Dust of the Furnaces at Low Moor, Va. Amer- 
Inst. Min. Eng. Oct. 1838. Cadmium was also found years ago in an old furnace 
at Ancram, N. Y. 
