THE BOHEMIAN RANGE. 181 
some of the grander structural problems that present themselves to the stu- 
dent of Lake Superior geology. A week’s study in the field, however, of 
the region about Lac La Belle, and Mount Houghton, and subsequent ex- 
amination of a large number of thin sections, have served to convince me, 
not only that the rocks of the Bohemian Range are an integral part of the 
Keweenaw Series, but also that they are—-with the exception of the 
brick-red augite-syenites, and possibly also of the orthoclase-gabbro of 
Mount Bohemia—distinctly bedded; that their rounded contours and lack 
of stairlike structure are due to a very high northern dip as contrasted with 
the flat dips of the more northern belts; that no anticlinal axis exists; that 
the contrast between these rocks and those of the more northern belts has 
been greatly exaggerated; that those rocks of this series which appear pe- 
euliar, viz: quartzose porphyry, and orthoclase-bearing gabbro, are just 
such as are repeatedly to be seen at similarly low horizons throughout the 
entire extent of the formation; and that interstratified with these, and pre- 
dominating over them, are luster-mottled melaphyrs, fine-grained diabases, 
diabase pseud-amygdaloids, true amygdaloids and porphyry-conglomerates, 
in no way different from the more northern rocks of Keweenaw Point. 
The opportunities for studying the structure of the Bohemian Range in 
the vicinity of Lac La Belle are very good. By following the south side 
of the range from the head of Lac La Belle a distance of seven or eight 
miles to the porphyry bluffs on the north shore of Béte Grise Bay, Sec. 29, 
T. 58, R. 28 W., one obtains gradually a nearly continuous cross-section 
of the range, while the large exposures on Mount Houghton and Mount 
Bohemia, and again on the road from Lac La Belle to the Delaware mine, 
help greatly towards a shorter and more direct cross-section. 
Among the most northern and at the same time most interesting of the 
belts of rocks which compose the Bohemian Range, using that name now to 
cover all of the line of elevations south of the valley of the Little Mon- 
treal River, is the red felsite which constitutes the bold point known as 
Mount Houghton. This mountain, whose summit is crossed by the west 
line of See. 24, T. 58, R. 29 W., at 6,250 feet north of the north shore of 
Béte Grise Bay, is one of the most prominent topographical features on 
Keweenaw Point. It reaches an altitude of 847 feet, a height which is 
