GEOLOGICAL EXPLOITATIONS AXI) LITER ATURE-I80O. 25 



the field iidtes of the linear surveyors, in wliicli inanvledg'es of iron-bearino- 

 rocks had been located. With the aid of those and their own observations 

 they presented in their first joint report a fairly good general view of the 

 iron district. They also constructed a map which giive the first inforniation 

 we possess of the distril)ution of the ore-bearing rocks. The rei)ort is 

 simply a synopsis; so it is limited to general statements. With reference 

 to the iron region, we quote (pji. G09-()l()): 



Oil refen-iug to the map wliicli accoiiipaiiics this .synop.sis it will be seen that 



the iroji occiu's iu a nietaiiiorpliie foiiiiatioii, bounded by two granite belts one ou 



tlie north and the other on the .south — and that it is prolonged westerly beyond the 

 Machigamig River. This formation consists of hornblende, talcose, and chlorite 

 slates, with associated beds of hornblende and felspar rocks, evidently trappean in 

 their origin. In that portion of the region drained by Carp and Dead rivers and 

 even in the head waters of the Escanaba, the trappean rocks rise in irregular knobs 

 and ridges from 100 to 200 feet above the general level of the country, and from 800 

 to 1,000 feet above the lake level. To the west and south of Machi-gumini (or Big 

 Lake) the ridges are less abrupt, and there are some townships where there is scarcely 

 a single exposure of the rock in place. 



A description of the ores is given, their banded character is nofed, and 

 the great abundance of good ore in the region is emphasized. Nothiu"- else 

 of interest concerning the iron region is given in the synopsis. 



On the map the color for the metamoriihic rocks of the Azoic system is 

 made to cover a large area of country which we now know to be underlain 

 by older rocks. The metamorphic series included the iron-bearing rocks, 

 but besides these it embraced also the "green-schists" north of the iron l^elt 

 jiroper, and many hornlileude-schists and mica-schists southeast tif Lake 

 Jlichigamme. Iu the metamor])hic area four colors are used to distinguish 

 the four rocks, quartz, saccluiroidal limestone, trappean rocks, and the undif- 

 ferentiated'schistose series. At the mouth of the Carp River there is mapped 

 a small area of sandstone, belonging at the base of the Silurian system. 

 The quartz is in ranges, beginning as two ridges at the lake shore on 1)oth 

 sides of the Carp River, uniting into one about F) miles inland, and continu- 

 ing as a single ridge to Teal Lake and 2 miles beyond. The saccharoidal 

 limestone is represented as several narrow bands occurring along the north 

 sides of the eastern quartz ridges. Presque Isle is colored for basalt, which. 



