14 THE PENOKEE lEON-BEAEING SERIES. 



iiiterveiiing slates. The same cuuclusiou is indicated in the following 

 remarks qmjted from this letter (p. 230): 



On crossing tlic southern edge of the ti'iip r;uigc, we no longer lind, on proceeding 

 south, a belt of Siindstoiie similar to that on the Tiorth, as is the case between the 

 Portage and the Ontonagon. The only rocks which we have found in place are 

 granite and greenstone; not, however, arranged in regular order, but scattered con- 

 fusedly without order of superposition or direction. Tlie whole country to the soutli, 

 as seen from any one of the high points of the trap range, :is tar as the eye can reach, 

 seems to be ahnost an unbroken plain. On traversing it, it is found to be made u]) of 

 alternate swanii)s and low ridges of granite and greenstone, which are sometimes 

 hidden by soil and covered with pine, hemlock, and especially sugar maple. Some- 

 times, again, the granite rocks rise with almost vertical walls, yet never to any con- 

 siderable height, from the midst of the swamps, and are covered only by thick moss. 

 It will be impossible to draw any line of demarcation between the granite and green- 

 stone rocks, since they occur together constantly, neither being eoulined to any 

 particular portion of the district. 



The whole of this country is almost inaccessible from its swampy nature ; neither 

 does it promise to be of any value for its mineral contents, since we have never fVnind 

 any other ores than a few scattered magnetic masses of iron ore and iron pyrites; 

 neither, hoAvever, in any considerable quantity. 



1850. 



Barnes (George O.). Diary of field work for the summer of 1847, in Report 

 on the Geological and T\Iiner;ilogical Siu'vey of the Mineral Lands of the United 

 States in the State of Michigan, by 0. T. Jackson, U. S. Geologist, Senate Docs., 

 1st sess., 31st Cong., ISlO-'oO, vol. in. No. 1, pt. in, pp. ;i71-(;0.5, also pp. 627-801. 



Although a tYirther and tiual report was published by Dr. Jackson in 

 1852, this one is essentially the closing report of his work, covering the 

 period up to tlie time of his resignation of the survey into the hands of 

 Messrs. Foster and Whitney. Mr. Barnes's diary of field work is given in 

 this rej)ort. The largei' ]);irt of the region west of Gogebic lake was at 

 the time without surveyed lines. His course of travel and his failure to 

 discover a series of iron-bearing slates have already been noted. Mr. 

 Barnes crossed the Gogebic belt once and made an extended trip in the 

 granite region farther south. Later in the same season (see diary pages 

 738-740) Mr. Barnes accompanied Whitney in his traverses of the Gogebic 

 district, and designated the positions of a number of rock exposures on the 

 lines followed. 



