76 TRANSACTIONS OF THE [J AN. 23 



This occurrence of iiorite, although clearly restricted in area, 

 is interesting for several reasons. It indicates in the first place, 

 an outcrop of this rock in the extended interval between Peeks- 

 kill on the north and Baltimore on the south, which was not 

 hitherto known to contain it. In Volume I of his Final Reports, 

 pp. 107-108, Professor Lesley remarks, with some surprise, on 

 the absence of the " Labradorite " rocks or Norian in this 

 Archaean belt. The rocks here mentioned are entirely analogous 

 to many in the Adirondacks. But I w^ould not wish to imply 

 anything of their geological age from their mineralogical 

 composition. They may be merely an intruded knob or large 

 dike. We have also in the Columbia College collections a slide 

 of a rock, which was collected by Dr. Britton from a cut on the 

 Ogden Mine Railroad north of Minnesiuk, N. J. It is a well 

 marked gabbro with a little hypersthene. The slide shows 

 plagioclase, green monoclinic pyroxene, greenish hornblende, 

 magnetite, apatite, and the little hypersthene referred to. 

 Probably other occurrences will be found in the great exposures 

 of the crystalline rocks of the Highlands. R. W. Raymond 

 has called attention to titaniferous ores in New Jersey at the 

 town of Bethlehem. (See discussion of paper by H. B. C. Nitze 

 on " Magnetic Iron Ores of Ashe County, North Carolina," at 

 the Baltimore meeting of the Institute of Mining Engineers, 

 February, 1872.) It would be quite natural from what we 

 know of these ores in the Adirondacks and in Sweden to find 

 them associated with rocks of the gabbro family. 



The second interesting point is that the minerals in the 

 limestone at the quarry are probably the result of contact 

 metamorphism wrought by the plutonic rock mass on the 

 neighboring limestone. While much the same series occurs in 

 the regionally metamorphosed linestones of Canada and else- 

 where, where no igneous rocks have been mentioned, the list 

 does present some striking similarities with those which have 

 been formed by contact action or limestones in many parts of 

 the world. Although few cases are recorded where these efiects 

 are due to rocks of the gabbro family, we have descriptions of 

 many such contacts of diorites, syenites and diabase in the 

 Tyrolese Alps, with which the Austrian geologists — Tschermak, 

 Reyer, Lepsius, and others — have made us familiar. Many of 

 the minerals mentioned above appear there, but in Pennsyl- 

 vania we lack vesuvianite, which is often characteristic of such 

 surroundings. G. H. Williams found at Stony Point on the 

 Hudson, a narrow strip of limestone between mica-diorite and 

 peridotite. It contained malacolite, light green hornblende, 

 zoisite, sphene and scapolite. We have all of these except 



