ORE DEPOSITS OF FRYER HILL. 491 



find evidences of the passage of the ore currents along these walls ; but 

 wherever they have been examined these evidences are conspicuously want- 

 ing. On the south flank the dike is generally separated from the ore body 

 by a barren zone, containing often, it is true, iron vein material, but evi- 

 dently of secondary origin. On the north flank the ore body extends up 

 to the dike, but it is strictly confined to the ore horizon, and does not extend 

 below that, the most that is found being a slight staining by iron oxides, 

 readily accounted for by the percolation of surface waters descending 

 through the ore horizon and carrying down some of its material with it. It 

 is unfortunate that a more conclusive test coul<J not be afforded by the cut- 

 ting of the dike at a considerable depth below the ore horizon, but as this 

 has not been done, we must reason from the evidence that is at hand. 



The apparently abnormal variation in the thickness of the ore horizon 

 is less readily accounted for, as has already been stated on page 446; but it 

 must be borne in mind that the data from which the outlines of formations 

 have been reconstructed are very limited and irregularly distributed, being 

 derived from drifts run for the sole object of following known ore bodies 

 and without any purpose of elucidating the structural conditions of the vari- 

 ous strata. 



The singular absence of. lead in the Lee ore body is another excep- 

 tional feature of this region. It seems hardly probable that, in a district 

 whose silver is so universally derived from argentiferous galena or its 

 decomposition products, in this little spot alone silver should have been 

 deposited by itself. The more natural explanation would seem to be, that 

 the deposit is entirely secondary, and the result of the leaching of a larger 

 body, now eroded off, by surface waters, which carried away the lead and 

 left the silver. The geological position of the ore body favors this idea; it 

 rests immediately on the Parting Quartzite, and therefore at the very base 

 of the ore horizon ; it is on the lower rim of a synclinal basin, which is known 

 to carry an immense amount of water that would naturally drain out over 

 its edges. It may be also that the absence of manganese would tend to the 

 formation of the more soluble sulphate of lead, rather than the carbonate, 

 which is generally found as the alteration product of galena in this dis- 

 trict. 



