124 KEMP'S ORE DEPOSITS. 



ranged in their orcler of probable age. They correspond in some 

 respects to Britton's grouping, but differ materially in others. 

 (G-eol of N. J., .1889, p. 30.) Four courses, or mine-belts, have 

 been recognized in New Jersey, the Rarnapo, the Passaic, the Mus- 

 conetcong, and the Pequest, in order from east to west. The 

 lenses strike northeast with the gneisses, and usually have, like 

 them, high dips. In addition they have also a so-called " pitch " 



FIG. 27a. FlG . 



FIGS. 27a and 276. Model of the Tilly Foster ore body. 27a, Top view, 



showing faulted shoulder. After F. S. Ruttmann, Trans. Amer. 



Inst. Min. Eng., XV. 79. 276, View of bottom of same. 



Photographed by J. F. Kemp from the model now 



at the School of Mines, Columbia College. 



along the strike, so that they run diagonally down the dip. They 

 have been observed to pitch northeast with an easterly dip and 

 southwest with a westerly. Either by the overlapping of lenses 

 or by an approximation to an elongated bed, they sometimes, as at 

 Hibernia, extend a mile or more in unbroken series. Again, they 

 may be almost circular in cross section (Hurd mine). At Frank- 

 lin Furnace one is found in crystalline limestone. 1 



1 E. S. Breidenbaugh, "On the Minerals Found at the Tilly Foster 

 Mine, New York," Amer. Jour. ScL, iii., VI. 207. J. F. Kemp, " Diorite 



