230 Blake — Progress . of Geological Surveys in Wisconsin. 
driftless region led him were, briefly stated, that the region 
existed as an island rising above the level of the ocean during the 
drift epoch, and consequently escaped the deposition of drift 
boulders and other materials characterizing the drift deposit of 
adjoining regions. In forming this conclusion it will be noted 
that he held the then prevalent opinion of the diluvial origin of 
drift deposits, and that he did not entertain the idea of their 
glacial origin and distribution. He carefully and correctly de¬ 
scribes the phenomena of chemical erosion or gradual solution 
of the surface of the rocks and the accumulation on the surface 
of the less soluble portions, such as flint nodules and fragments, 
remarking that we never find them assorted in layers, or show- 
in g any indication of the action of currents of water, from 
which he concludes that the driftless region must have formed 
an island at the time “when the great currents from the north 
were bringing down the detrital materials which were spread 
over so vast an area in the northern hemisphere. ”* 
He directs attention to the fact that in the lead region the 
line of water-shed is an exact east and west one, and that it is 
pretty evident “that this portion of the surface of the state has 
been elevated parallel to the great north and south axis which 
has determined the geological features.” (P. 127.) 
Professor Whitney formulated a theory of the original depo¬ 
sition of the ores from the waters of the ocean in certain areas 
determined by the presence of marine plants. 
However probable this may be, it fails to explain the sharply 
defined linear distribution of the ores, and the origin of what 
we may term the vein system. 
Professor Chamberlin’s theory of undulations as opposed to 
f aultiug, if accepted, leads us substantially to the conclusion 
that the distribution of the cres is due to the structure, or 
rather to the disturbance of the strata. This implies that the 
deposits really have the nature of lodes, and that the same causes 
may produce like effects in all of the beds whose chemical com¬ 
position is favorable to the deposition of ores. It is, therefore 
favorable to the view that ore deposits may be found in te 
* Report 1862, p. 123. 
