On the Zinc Mines of Franklin, N. J. 



257 



rnginous limestone, very heavy, but easily disintegrating, being a 

 coarse crystalline variety ; this is from two to six inches thick. 

 Third, we reach a bed of pure Franklinite, more or less crystal- 

 lized, sometimes perfectly so, either in the cavities, or at the line 

 of junction with the ferruginous limestone, — the hmestone being 

 no more united with the Franklinite than it is with the mixed 

 materials of the first bed : this bed is from ten to twenty feet in 

 thickness. Succeeding this, we have nothing but the contiguous 

 gangue of limestone, until it reaches the gneiss farther to the 

 westward. The following diagram represents a section of these 

 beds at Sterling, near the horizontal gallery made by Mr. Hitz. 

 The beds are not the widest at this place, but their position is 

 the most favorable for observation and exploration. 



B I a c7<r .L I Titestojie^ 

 I'^^^^^^^^YnW^^^K?^ 0^^<^ of Zinc. 



Now at Franklin, as a proof of the singular regularity of these 

 associated beds, the order is not reversed, though it appears to be. 

 Our position is only reversed, and we see the beds from the west, 

 instead of the east. Of course, the outer bed nearest to the val- 

 ley, is the immense bed of pure Franklinite, the inner one being 

 the mixed red oxide, thereby rendering the mining operations 

 less favorable here than at Sterling. 



The most singular feature in these beds (perhaps it is no where 

 else in the world more conspicuous) is the beautiful and perfectly 

 distinct separation observed between them, along the whole line 

 of their contact. This circumstance renders it difficult to ex- 

 plain the origin of these deposits, either from infiltration above 

 or injection beneath, unless we refer them to different epochs, 

 and suppose a suspension or change in the cause which produced 

 them, so that successive intrusions of the matter now filling the 

 original opening, could have taken place. That one must have 

 been deposited after the other, we are as certain as we are that 

 one mineral vein which crosses another must be the newest. It 

 is not my intention, however, to enter much into theory on this 



