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THE PRE-CAMBRIAN GEOLOGY OF PORT 

 ARTHUR DISTRICT. 



History of Exploration. 



Port Arthur district has been widely known for many 

 years because of its silver mines, which were at one time 

 large producers. Of these, Silver Islet mine was the most 

 noted, not only for the amount of silver obtained from it, 

 but also for the Frue vanner which was invented by men 

 connected with the mine and first used in the concentration 

 of Silver Islet ore. 



The first important description of this district was 

 prepared by Sir. W. E. Logan (1). This was followed by 

 a more extended description and a geological map by the 

 same author at a later date. (2). 



The explorations of Dr. R. Bell along the north shore of 

 Lake Superior in 1869 (3) added materially to our knowledge 

 of the rocks of this region, but unfortunately the map 

 accompanying the report shows no geology so that it is 

 difficult to estimate the scope of his work. 



The first important work dealing in detail with the 

 silver deposits was done by E. D. Ingall (4), who shows in 

 a sketch map the geological boundaries as then known 

 and the location of the mines. He also prepared a geological 

 and topographical map of Silver Mountain mining district 

 which gives the essential features of the geology of this 

 region. A resume of this report is given by Dr. W. G. 

 Miller (5) to show the similarity of the silver deposits of 

 Cobalt with those of Port Arthur district. 



The latest work in this region was done by Dr. N. L. 

 Bowen (6), whose report supplements that of Mr. Ingall 

 by including the later mine development. 



Geology of the District. 



The geology of Port Arthur district is simpler than it is 

 near Loon lake, because of the absence of the Keewatin 

 and Lower Huronian . Only the Pleistocene, Keweenawan 

 and Upper Huronian or Animikie occur in the immediate vi- 

 cinity of Port Arthur. Laurentian and Lower Huronian 

 rocks are to be found within four miles (6-4 km.) to the 

 north of the city but are not exposed within the area visited 

 by the excursion. 



