GEOLOGICAL EXPLOKATIOXS AND LITER ATUltE—]85(». 17 



of Douglass llougliton, during the years 1845 and 184G. Houghton 

 instructed his assistants to observe the ledges on their lines df traverse, 

 1 mile apart, running east and west and north and south, to report their 

 character, and to collect specimens from them. The repoi-ts of ]\lessrs. 

 Burt and Hubbard are based on these observations. Geolog}', of course, 

 was of secondary interest to these surveyors, and yet tlieir geological 

 work has been of great value to all later g'eologists who have made 

 excursions into the district surveyed. Foster and Whitney used the linear 

 surveys to great advantage in prosecuting tlieir explorations, and all 

 geologists who have followed these two have been guided to important 

 outcrops by the notes of tlie surveyors. These notes, as has already been 

 mentioned, are printed in the same volume of the Government records as 

 the reports of Jackson and of Foster and Whitne}^, but since the latter 

 gentlemen made use of them, it is but right that Messrs. Burt and Hubbard 

 should be given priority in a discussion of the literature of the region. 

 Consequently, in this chapter their reports are given precedence of the 

 reports of Jackson and Whitney, although appearing later in the same 

 volume that contains the reports of these latter gentlemen. 



Burt, Wm. A. Topography and geology of the survey, with reference to mines 

 and minerals, of a district of township lines south of Lake Superior. 31st Congress, 

 1st session, 1849-50. Senate Documents, Vol. Ill, No. 1, pages 811-832. With map, 

 opposite page 880. 



Burt, as the result of his first yeai-'s survey, divided the rocks seen by 

 him during his journeys along the section lines into five principal grou])s: 

 the primary rocks, the traps, the conglomerates, the sandstones, and the 

 slates. The primary rocks, including the metamorphic ones, he found 

 generally a little inland, with the metamorphic rocks flanking the other 

 members of the primary series on the south. The rock to the north is 

 "sieuite," or " sienite granite." Hornblende is a moi'e frequent constituent 

 than mica, hence "sienite" is the predominant rock type. Greenstone 

 intrusives and ^eins of quartz and feldspar cut the primary rocks in all 

 directions. In the metamorphic series south of the primary granite and 



MON XXVIII 2 



