VOLCANICS OF THE MICHIGAMME DISTRICT. 803 
are connected around the ellipse both to the north and south, 
forming a belt completely encircling it. The volcanics are in 
turn enclosed by a zone of sedimentaries, for the most part quartz- 
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PLATE I. 
Preliminary map of part of the Michigamme district. Scale I in to 4 miles. 
ite and slate, which is throughout characterized by the greate1 
or less amount of iron which it contains. It is known as the 
Michigamme jasper, from its typical development at Michigamme 
