40 BULLETIN OF THE UNIVERSITY OF WISCONSIN 



in a slightly north of west direction. In Sections 16 and 21 

 the thickest portion of the eruptive mass is found, for 

 its contact with the quartzite at this place is distinctly- 

 shown near the northern boundary of the southeast i of 

 Sec. 21, from whence it extends north forming a broad ridge 

 cut by ravines, with its northern limit near the middle of 

 the southeast i of the southeast i of Sec. 16. 



It is apparent that Irving did not find the keratophyre 

 extending as far east or as far west as a closer study of the 

 area reveals^ for it is described as only reaching from the 

 Narrows to the south side of Sec. 16. 



The Contact. — The contact between the eruptive rock and 

 the quartzite is well defined, except where a bed of soil 

 overlies it. At the eastern end of the area in Sees. 22 and 

 23, where the keratophyre occurs as a narrow strip, the 

 quartzite is of a higher altitude than the keratophyre, and 

 stands out as a vertical cliff from ten to thirty feet high. 

 In the region from the center of Sec. 21 eastward, the con- 

 tact is easily made out, and ib is seen that its direction 

 conforms very closely with the strike of the underlying 

 quartzite, which is slightly south of east. From the cen- 

 ter of Sec. 21 across the greater part of the northwest i 

 of this section, the contact was not seen, but it was clearly 

 made out at the boundary of Sees. 20 and 21, near the 

 southwest corner of the northwest i of the northwest 

 I of Sec. 21. From this place eastward the actual con- 

 tact was not seen, but many schistose blocks of keratophyre 

 were found near the outcropping quartzite, and as the 

 keratophyre was found in situ in the northwest i of the 

 northwest i of Sec. 20, the contact is thought to be very 

 near the line indicated upon the map. The eruptive rock 

 at the contact occurs as schist, but the quartzite forms 

 massive beds, and is fresh and unaltered. Dikes and veins 

 from the eruptive rock were closely searched for the whole 

 length of the ridge at the contact, with the thought that 

 the eruptive mass might be intrusive and not extrusive, 

 but no such phenomena were found to occur. 



