BONE LAKE CRYSTALLINE SCHISTS. 149 



soutlieast, it gradually narrows, until in sec. 36, T. 46 N., E.. 32 W., the 

 eastern limit of tlie area studied by me, it is only about lialf a mile wide. 

 ExcejDt in the vicinity of Bone Lake, where erosion has uncovered some 

 of the knobs, outcrops are very scarce, since the drift is very heavy, 

 and the drainage is poorly developed. 



FIELD EVIDENCE OF CONNECTION WITH THE VOLCANICS. 



If one examines attentively the Hemlock formation in its typical 

 development, beginning, saj*, in sec. 27, T. 45 N., R. 33 W., and following 

 its northward extension through sees. 22, 16, and 15 of the same township, 

 he will observe instances of banding in the tuffs and of schistosity in the 

 am}-gdaloidal lavas and pyroclastics. The strikes and dips of the primary 

 and secondar}' structures approximately coincide, both having a general 

 north-south strike and dipping high to the west. Throughout this area, 

 however, the unniistakable massi"\-e volcanics are the predominant rocks. 

 Continuing the examination farther north into sec. 34, T. 46 N., R. 33 W., 

 rocks are found which possess almost invariably a strongly marked schis- 

 tosity, but with their volcanic origin cleaidy shown by the flattened amyg- 

 dules. This is also true for the exposures east of this place on the under 

 side of the Hemlock belt, in sec. 31, T. 46 N., R. 32 W. The strike of the 

 schistosity of the amygdaloids varies from N. 30° to 70° E., and the dip is 

 high to the northwest. Farther along this belt to the northeast, in sec. 24, 

 T. 46 N., R. 33 W., schistose pyroclastics were observed striking N. 80° E. 

 The original characters of these pyroclastics liave been almost entirely 

 obliterated. The exposures next to the east in sec. 16, T. 46 N., R. 32 W., 

 possess all the characters of crystalline schists. Somewhat farther east, 

 however, associated with these schists are isolated outcrops in which traces 

 of flow structure and remnants of amygdules were observed, and, in some, 

 traces of igneous textures were seen under the microscope. The schistosity 

 of these rocks strikes for the most part south of east, varying from N. 65° 

 to 80° W. and dipping to the nortiieast. Following the belt as it now turns 

 to the southeast, the crystalline schist characters prevail, the volcanic char- 

 acters being obliterated. The schistosity at the same time bends farther 

 around to the southeast, pointing toward the continuation of this area of 

 volcanics to the southeast, outside of the area studied. 



From field observations the conclusion seems necessary that these 



