The MIsKoirr! Le((<l xiul Zinc Deposits. — Roherfsun. 247 
nesium biesirbonute t(i ettect this. Besides this, the crevice 
deposits, ivhieh diminish in size as depth is reached, indicate 
that they were tilled from above. Finally, the decay of large 
(piantities of rock would give rise to correspondingly large 
bodies of ore, thus explaining the association of bulky depos- 
its such as lead and zinc, with the comparatively soluble 
limestones. 
Coming down to evidences of a more local nature we note 
that the large deposits of the southwest occur on the border 
of the Coal Measures. On examining the geological map of 
the state a tongue of Lower Carboniferous rocks will be no- 
ticed, extending to the eastward. This was probably the site 
of an estuary, through which large (juantitiesof water derived 
from the central and eastern parts of tlie area flowed, contain- 
ing the products of decomposition of the magnesian limestones 
of those sections. Thus was the material supplied. During 
the Coal Measure epoch an immense amount of decaying or- 
ganic matter supplied the most perfect means for the reduc- 
tion of the mineral in solution. The ample drainage con- 
stanth^ kept up the supply of metalliferous solutions anil the 
deposition probabl}' took place rapidl}". 
The crevice-shaped cavities were tilled by similar solutions 
and were probably deposited in a similar manner h\ the aid 
of organic matter. 
The disseminated deposits of the southeast are more ditticult 
to explain. In general they are found in an open porous 
rock, which is probably one of the chief causes of their for- 
mations. In addition to this, the occurrence of more or less 
organic matter in the rock has had some intluence, and the 
presence of shale beds has restricted and directed the tlow of 
solutions. The crevices frequently found in these mines have 
been, in all likelihood, the avenues through which the solu- 
tions traveled in reaching the shallower of these deposits. 
This is evidenced by the fre(iuent occurrence of galena in 
them. The deeper deposits of Flat Kiver, however, 
cannot he readily referred to these crevices, on account of 
their narrowing and dying out in depth. There is, however, 
underl3nng these dej^osits a bed of sandstfuie, open, porous, 
and water-bearing, which jnight be suggested as a soluticni 
carrier. Tlie water in this l)ed is uiuler sullicient head to 
