PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 261 



Porphyryte. Diabase.] 



between the nicols. This magmatic base is brownish with disseminated hematite 

 and surrounds the small microliths. The olivines are probably the oldest crystals in 

 the slide, as they are the largest, but they are wholly altered and are either opaque 

 with ferruginous matter or light green and nearly isotropic with the usual product 

 of such alteration. The plagioclases are small, blurred, apparently broken and so 

 indefinite as to render their specific determination almost impossible. The minute 

 brightly colored points which are presumed to be augite are scattered promiscuously 

 through the slide, but seem to cluster most numerously in the vicinity of the altered 

 olivines, a fact which casts doubt on their supposed augitic nature, but they resemble, 

 except for being much finer, the fine augites that appear in several other fine-grained 

 basic rocks of the region. One section. 



Aye. Cabotian. N. H. w. 



No. 214. PORPHYRYTE. ( Quartziferoim. ) 



Forms a low inconspicuous outcrop, runs along two or three hundred feet, dipping a little south of east, 

 about one-fourth of a mile west of Fish Hook point. 

 Ref. Annual Report, ix, pages 54, 55. 



Meg. More firm and siliceous than No. 213, and showing a few quartz phenocrysts. 



Mic. More completely crystalline, with a little pegmatitic quartz; also calcite 

 and epidote. One section. 



Age. Cabotian. 



Remark. This rock seems to approach very near the rocks Nos. 127 and 129, at 

 Beaver bay, and perhaps has the same origin and date. The occurrence in the lake, 

 off shore, opposite rocks Nos. 214 and 215, of a basaltic intrusive, may have some 

 bearing on the date and origin of this intermediate rock. N. H. w. 



No. 215. PORPHYRYTE. ( Quartzlferaus. ) 



Near No. 214, at Fish Hook point. 

 Ref. Annual Report, ix, pages 54, 55. 



This is also an intermediate rock, there being more or less secondary silica 

 diffused through it, due probably to deep-seated contact with acid rocks. 



Age. Cabotian. N. H. w. 



No. 216. DIABASE. 



"It is a greenish-brown rock with curling internal structure, containing quartz and amethystine nests, from 

 the westerly of the two little points west of Brul6 river, and before reaching either island, where a little stream 

 enters the lake. It is a short outcrop rising about five feet in the midst of a red beach. This is an igneous rock; 

 and the next point is of the same, also the little island off it, which is in the line of bearing." 

 . Ref. Annual Report, ix, page 55. 



Meg. The hand sample shows a rather fine-grained diabasic rock holding a 

 few small areas of chalcedony or of chalcedony and quartz. Along joints a small 

 amount of saponite is present. 



