193 



are the most striking feature of this rock. These are smoothly- 

 rounded, presenting botryoidal surfaces, very rarely nearly 

 spherical, but usually much extended in planes parallel with 

 the bedding. They are of all sizes up to a foot or more in 

 length, and one to two inches wide, and occur only along 

 certain definite planes, appearing on the surface as parallel 

 lines or strings of vesicles". They contain more or less min- 

 eral matter, concentrically arranged ; but the larger ones 

 especially are seldom entirely filled. The minerals which I 

 have observed are quartz, epidote, calcite, asbestus, and 

 chlorite. The epidote is most abundant, though scarcely ever 

 pure ; while the asbestus and chlorite are mainly confined to 

 narrow veins occupying joints in the rock. There can be no 

 doubt that this coarse amygdaloidal structure is the result 

 of igneous action, the source of heat being the adjacent 

 granite. Both the amygdaloidal structure and the cleavage are 

 found principally in the purplish-brown slate, and the former 

 diminishes sensibly as we recede from the granite. Interstrati- 

 fied with these grayish and brownish slates are several thin beds, 

 six inches to two feet thick, of white or greenish- white lime- 

 stone. This rock, too, is somewhat epidotic and amygdaloidal ; 

 and contains in some parts small quantities of a dark mineral, 

 with metallic lustre, resembling galena. 



After examining the rocks at Mill Cove, I returned to Hay- 

 ward's Creek, for the purpose of comparing the two localities. 

 Almost the first exposure outside of the trilobite quarry, follow- 

 ing the shore to the north-west, shows the bluish-gray slate of the 

 quarry interstratified with a brownish variety identical with that 

 at Mill Cove. At this point the dip is steep to the north : but 

 the slate shows no special alteration, although traversed by 

 dykes of diorite. Toward the granite on the south and west, 

 however, as noticed by previous observers, the slate is decidedly 

 indurated ; it is more or less epidotic, and in its hardness 

 approaches novaculite. As at Mill Cove, the slate is changed 

 by contact with the granite ; but in a different manner, the 

 amygdaloidal structure not apjjcaring. 



OCCAS. PAPERS B. S. N. H. — III. 13 



