184 



F 0 R M ATIONS OP 



The great geological formations of that part of the District, are crystalline and 

 metamorphic schists, penetrated by granitic and syenitic ranges, the general bearing 

 of which is northeast and southwest, deviating in a slight southerly curve as they 

 reach the Mississippi and the St. Peter's, in the southern part of Minnesota. The 

 rocks composing these ranges have, for the most part, a moderate elevation above 

 the general drainage of the country, though somewhat greater than through most 

 parts of the interior of the District. An idea of the features of the country may be 

 obtained from the sketch at the head of the previous paragraph, taken at a 

 locality known to the Canadian voyageurs as the Decharge de la Cave. 



The most elevated portion of the formation lies along the chain of lakes situated 

 between longitudes 91° and 92°, where the summits of the hills are, at a few points, 

 several hundred feet above the adjacent lakes. 



Towards the extreme northern boundary of the United States, amidst the nume- 

 rous islands of the Lake of the Woods, semi-crystalline, magnesian slates prevail, 

 assuming, locally, gray and silvery white tints, similar in composition to some of 

 the slates of the Valley of the Levantine, near Mount St. Gothard, in Switzerland. 

 The occasional protrusions of granite are frequently reticulated by a complete net- 

 work of veins of quartz, felspar, and graphic granite, and the former mineral often 

 traverses the adjacent slates. 



The most elevated range which we passed over, was on the trail leading from 

 the Prairie Portage to Cold- Water Lake. In view of that lake, the scenery is 

 abrupt and exceedingly romantic, as may be observed from the subjoined cut. 



GRANITIC AND SYENITIC RANGES, COLD-WATER LAKE. 



This view was taken from our camping-ground, at the head of the valley, looking 

 over the precipitous descent towards the northeast, and rivets the attention the 

 more, since it appears in striking contrast to the flat bogs and marshes which we 

 had just passed over, on the Savanna Portage, a few miles back, and the multitude 

 of low islands we had previously threaded before entering the Savanna River, on 

 the northern slope of the same water-shed. 



