572 BEPORT OF NATIONAL MUSEUM, 1904. 



derived b}^ wave action from the reef, the compact strata being deeper 

 quiet- water deposits of the same material. 



Chamberlin also investigated the ore deposits of the southeastern 

 part of the State, and discussed thoroughly the problems involved in 

 the origin of the ores, disagreeing in many minor points with both 

 Doctors Owen and Whitney. The crevices in which the ores occur he 

 believed to have originated primarily in the folding of the rocks by 

 lateral pressure. He pointed out that the ore beds occur mainly in 

 basin-like depressions and argued that the ore material, originally in 

 solution in sea water, was deposited contemporaneously with the lime- 

 stone through the action of sulphureted vapors given off by the 

 decomposition of organic matter, and that, after the elevation of the 

 beds above sea level, percolating meteoric waters oxidized and dis- 

 solved the ore once more and carried it into the fissures above noted, 

 where it was the second time precipitated as sulphides. Fourteen- 

 huudredths of 1 per cent of ore material disseminated throughout 

 LOO feet in depth of the ore-bearing limestone would, he pointed out, 

 be sufficient to have formed all the deposits as they now exist. He 

 did not agree with Whitney in assuming that the oceanic waters of 

 early geologic periods were richer in metallic salts than those of Jater 

 data, instancing in support of his argument the fact that the ore-bearing 

 beds were in many cases really poorer in organic matter than those 

 which were nonmetalliferous and more ancient. This criticism did not, 

 however, affect the general principle as laid down by Whitney. With 

 his predecessors he doubted the probability of the existence of work- 

 able deposits of ore in the Lower Magnesian limestone. 



Volume I of the reports of this survey was designed as a general 

 treatise on the geology of the State, suited to the wants of explorers, 

 miners, landowners, and manufacturers. In this Chamberlin stated 

 his belief that the original source of the Keweenawan copper ore was 

 the igneous rocks, from whence it has been concentrated through the 

 agency of permeating atmospheric waters. To quote his own words, 

 he believed — 



First, that the metals, copper and silver, were primitively constituents of the rocks 

 that were melted to produce the lavas which formed the trappean sheets of the 

 formation; second, that they were brought up and spread out, commingled with 

 the molten rock material; third, that they were chemically extracted thence by per- 

 colating waters and concentrated in the porous belts or fissures of the formation, 

 giving rise to the exceptionally rich deposits for which the formation is famous; and 

 fourth, that the surface disintegration of portions exposed in the latter part of the 

 period yielded metallic ingredients to the adjacent sea, frem whence they were 

 extracted by organic agencies, giving rise to impregnated sediments, which, in turn, 

 through subsequent concentrations, gave rise to other copper and silver deposits, 

 among which are to be reckoned the later metallic horizons of the Lake Superior 

 region and possibly elsewhere. 



Naturally, the subject of the drift was treated in considerable detail! 

 The Glacial period was divided into the Terrace or Fluviatile epoch, 



