552 OGILVIE 



green hornblende without orientation, with the diabasic texture 

 in part interfered with by the green hornblende which cuts the 

 feldspar boundaries. 



As indicated on the map, there is another outcrop of this dike 

 to the west. This is a small area in the woods, no other rock 

 being visible and a few feet only of the diabase exposed. Thin 

 sections show this to be identical with the shore exposure, but 

 of coarser grain. It is evident that a large proportion of the 

 width of the dike is covered by vegetation, since its grain is too 

 coarse to be produced in the width exposed. 



An estimation of the contents of these dikes leaves no reason- 

 able room for doubt that they would all fall into the subrang 

 auvergnose. The Cape Newagen dike forms a connecting link 

 between these dikes and the older complex. It is practically 

 intermediate between the diabases and the hornblende schist of 

 this same subrang. 



The smaller dikes, although diabases, present notable differ- 

 ences, from all of the above and from each other. On Capitol 

 Island are two, of which one has a nearly east and west, the other 

 a nearly north and south trend. The first mentioned has a 

 strike of N. 8o° E. and is exposed on and near the western shore. 

 A gorge on the mainland of Southport indicates that the dike 

 continues there, but no material could- be found in the latter 

 locality. Microscopically it is found to be a porphyritic diabase, 

 with phenocrysts of plagioclase with less augite and olivine. 

 In the ground-mass are plagioclase and augite. Its affinity is 

 with the east and west large dikes (auvergnose), but there is a 

 larger proportion of augite in the ground-mass and the diabasic 

 texture is not perfect. The plagioclase phenocysts are older 

 than the femic ones and sometimes are entirely surrounded 

 by them. In such occurrences the edges of the plagioclase are 

 corroded and the femic silicate enters it irregularly, notably along 

 the twinning planes. Titanite and grains of magnetite are 

 present in notable amount. Much of the olivine is altered to ' 

 brownish green serpentine and a carbonate. 



The north and south dike of Capitol Island is exposed in a 

 bay on the southern shore, and after extending about one hundred 

 feet inland the strike turns to N. 20 E. Microscopically it is 



