1895. | NEW YORK ACADEMY OF SCIENCES. 215 
A UGITE—PORPHYRITE. 
The dykes in Sub-carboniferous sandstone at Poverty Hall 
Point appear to be of this rock. The phenocrysts are chiefly 
augite, the larger ones being entirely, the smaller ones frequently 
chloritized. They present the usual short stout crystals charac- 
teristic of augite, and are quite abundant. Augite occurs also 
in the groundmass, but is mostly destroyed. JMagnetite is 
abundant in small crystals. Olivine phenocrysts occur rarely. 
The plagioclase is confined to the groundmass and is in small 
lath shaped crystals. A micaceous mineral occurring in small 
plates in the groundmass is perhaps an altered biotite, and is 
quite abundant. . 
With these Carboniferous dykes may be placed from litholog- 
ical resemblance spec. 148, a dyke in the volcanic series at Lily 
Lake, known as labradorite-porphyrite. It contains large phen- 
ocrysts of completely altered feldspar. Spec. 251 is perhaps 
also related, showing augite and occasional feldspar phenocrysts 
and a much altered groundmass which contains a great abund- 
ance of plates of altered biotite (?) in a feldspathic base now 
apparently recrystallized and granular. 
ADDITIONAL NOTES ON THE LAURENTIAN ROCKS. 
Some further notes may be made as to the Laurentian areas 
in a few places otside of the district studied last year ; though 
no general examination was made of them. 
A more massive gneiss than has yet been noticed occurs be- 
yond Sutton Station, on the Canadian Pacific Railway; it is 
strongly feldspathic, banded, and contains a bed of limestone. 
The intrusive granites occur both east and west of the mapped 
district. To the southwest are also large masses of granite of a 
different type, non-porphyritic, much altered, and perhaps older 
than the Indiantown granite. At Musquash the contact is ex- 
posed between it and the Devono-Silurian limestone. The gran- 
ite is here clearly seen to be the older rock. 
The gabbro (olivine-norite) hill north of Dolin’s Lake presents 
less variation in feldspar contents than the small Indiantown 
exposure. Its grain varies greatly, crystals being sometimes 2’ 
across, sometimes finely granular and almost ophitic (Pl. XV., 
Fig. 1), as in spec. 474 “This section fails to show olivine; it 
is made up of colorless. augite, weakly pleochroic hypersthene, 
biotite, and basic plagioclase, the latter giving a maximum extine- 
tion of about 36°, and occurring in more or less lath-shaped 
crystals, which however do not distinctly appear to be older than 
the bisilicates, and are certainly in part younger. The biotite is 
later than much of the feldspar. Magnetite and apatite occur 
