244 REPORT OF NATIONAL MUSEUM, 1904. 



factorily determine, though its position seemed to him to indicate a 

 near alliance to the " Old red sandstone.'' a 



He described the finding of the large block of native copper (now in 

 the IT. S. National Museum in Washington), upon the edge of the 

 Ontonagon River, giving a picture and offering some remarks on the 

 probable origin of the same. In his report to Secretary J. C. Cal- 

 houn, under this same date, made with reference to the copper mines 

 of Lake Superior, Schoolcraft dwelt in some detail upon the occur- 

 rence of frequent masses of drift copper, but stated that no body of 

 the metal sumcientl} T extensive to mine profitably had been discovered. 

 He, however, regarded it as probable that a more intimate knowledge 

 of the resources of the country might result in the discovery of valu- 

 able ores of copper, in the working of which ""occasional masses and 

 veins of the native metal may materially enhance the advantage of 

 mining." This prediction, it is scarcely necessary to say, has been 

 abundantly verified. 



Writing on the prevailing theories as to the origin and distribution 

 of metals and gems, he remarked, "There is no reason that can be 

 drawn from philosophical investigations to prove that these substances 

 may not be abundantly found in the climates of the north, even upon 

 the banks of the frozen ocean," their distribution being apparently 

 wholly independent of climatic conditions. 



The Dubuque lead ore he described as occurring in detached masses 

 in the ocherous alluvial soil resting upon a calcareous rock referable 

 to the Transition class (in the revision of his work, published in 1832, 

 he made this Carboniferous), and also in veins penetrating the rock. 

 The relationship existing between the rock and the residual clay did 

 not seem, however, to have been recognized/ 



The presence of extensive beds of coal about 40 miles southwest of 

 Chicago, on the Fox River, was noted. The fact that bricks, made 

 from clay occurring near Chicago, turned white was* also noted, and 

 explained on the ground that they were lacking in iron oxides/ 



In his "Travels" Schoolcraft advanced the idea that there had been 

 at some former period an obstruction in the channel of the Mississippi 

 River at or near Grand Tower, in southern Illinois, whereby there 

 was produced a stagnation of the current at an elevation of about L30 



" The correct position of this sandstone remained long a matter of doubt and dis- 

 pute. It is now considered as of Potsdam age. 



f > Since this mode of occurrence was referred to by subsequent explorers, it may be 

 well to state here that the ore was originally in the limestone, from which it was 

 liberated by decomposition and left to accumulate in the residual clay, representing 

 the insoluble constituents. 



'This has since been shown to be an error. These clays contain as much iron as 

 others that may burn red. It is probable that, in the process of tiring, this iron coin- 

 bines to form an iron-linie-magnesian silicate and is not oxidized to the extent of 

 imparting the common brick-red color. 



