GKOLOGICAL EXPLORATIONS AND LITERATURE— 1848. 15 



of the Treasury Department. Thereupon Dr. C. T. Jackson was aj)pointe(l 

 by the Acting- Secretary of the Treasury "to make a geological survey of 

 the Lake Superior district, in JMichigan." Dr. Locke was selected b\' Dr. 

 Jackson to be assistant geologist to take cliarge of one of the exploring 

 parties, whose duty was to examine that })ortion of the south shore of the 

 lake east of Keweenaw Point. His report was published in 1848, although 

 the reports of Jackson's other assistants did not appear until the records 

 of the following Congress were printed, and not until after the appearance of 

 the re})orts of the linear surveyors, whose work was concluded and whose 

 results were probably known to Dr. Locke before he took the field. These 

 latter reports take precedence in point of time, although they were not 

 given to the public until after Locke's report. 



Li his report Locke mentioned pure iron ore as occurring on Presque 

 Isle. He further remarks (p. 187): 



The region drained by Dead and Carp rivers is full of interest, and, geologically, 

 is a "compact country," presenting a great variety in small distances. * * * |it 

 consists of] knobs of greenstone and augitic traj), surrounded by altered sandstone and 

 slates. Perhaps not so much "knobs" as ridges. The sandstone is changed almost into 

 quartz, and the slates occur so nuich transformed that at some points it is difficult to 

 distinguish them from trap. * * * This region has been called the " Cornwall of 

 America," in reference to its general geology. It has been said that there are rocks 

 there suitable to contain gold, silver, copper, lead, &c. So far as I have observed, it 

 is a gold region " all but ihe gold," a silver region without silver, and acop])er region 

 with veins and bunches of ore so thin and scattered as to be luiprotitable for working. 



The author of the report refers to the ore of the Jackson Iron Com- 

 pany as similar to that of Missouri, and aimounces the discovery of some 

 very pure iron ore along the western edges of Ts. 47 and 48 N., R. 2(5 W., 

 and in the contiguous towns. He also identifies the "granite" of the 

 Michigan map (probabh' referring to the map afterward published by 

 the linear surveyors) as a |)orphvritic syenite. 



Channing, Wm. F. Dr. Channing's synopsis of the survey in charge of Dr. John 

 Locke. (Second section.) 30th Congress, 1st session, 1847-48. Senate Documents, 

 Vol. II, No. 2, pages 207-208. 



Locke's report is so badly written that it is fortunate for its author's 

 rejaitation as a geologist that he had with him as "first subagent" Dr. 



