194 Mining Report JVb. 1. [Nov., 



heavy beds of primary limestone are not uncommon, some of which 

 are sufficiently pure for lime. One of these we discovered about 

 two miles south of Clintonville, and beneath a remarkably heavy 

 precipice of gray granite. Some geologists have been disposed 

 to regard these beds and veins of limestone, for it occurs in both 

 forms, as old sedimentary deposits of limestone over which granite 

 has been poured in a moulten state. That such an occurrence 

 might happen, there is no doubt, and that granite more recent 

 than our Trenton limestone exists no geologist of the present de- 

 nies. Still, that these beds of limestone are sedimentary depos- 

 ites and have been altered no one can prove. Indeed the facts all 

 go to show that the limestone is an unstratified rock, and is anal- 

 ogous to granite, and belongs to the primary class, is sufficiently 

 proved. The phenomena supporting this view of the subject have 

 been fully given in geological reports of the second Geological 

 District of New York. 



Another interesting feature of this region, though by no means 

 confined to it, is the numerous trap dykes which traverse the work 

 in one principal direction, viz., to the northeast or some point be- 

 tween north and east. These dykes invariably cut across the veins 

 of ore, which they more or less disturb. It is apparently due en- 

 tirely to this disturbing force that the veins are forced out of 

 their usual course or direction; or in other words the expense and 

 hazard of working the veins, is incurred by the disturbances 

 which may be traced directly in many cases to the changes effect- 

 ed during the process of filling rents with molten matter from be- 

 neath. Undoubtedly the forces which first fissured the rock an- 

 terior to the time at which they were filled, produced the princi- 

 pal disturbance which miners complain of. However this may 

 be there seems to be much regularity in the disturbances as well 

 as in the direction of the veins and dykes. Hence the study of 

 these disturbances becomes a matter of considerable moment in a 

 practical point of view, for the phenomena of one vein are often 

 repeated in many, and what illustrates a system of veins, dykes 

 and disturbances of one district, illustrates also those of another. 



The surface of the rocks of this region is covered very exten- 

 sively with a fine gray sand, near the top of which are boulders 

 which come fiom the north and northeast. The contour of the 

 country is hilly. These hills are steep on all sides, but they are 

 not properly in ridges, but insulated hills, upon the tops of which 

 the vein of ore usually appears. It is rare indeed that a vein 

 appears in a valley, and though we may be satisfied that a given 

 one crosses a valley, still there it never appears. In depressions 

 between two given points, when a mine is w^orked, it rarely 

 reaches the surface. There is it is true a larger amount of earth 

 in valleys than upon hills, and this accumulation of earth may con- 



