120 GEOLOGICAL AND MINERALOGICAL NOTES. 



and the soda-microcline which are characteristic minerals 

 described by Professor Brogger as occurring in the augite- 

 syenite rocks of Norway. Thin sections prepared from 

 specimens collected on Pierce's island in Squam river have 

 the following mineral composition : Nos. 1, 2, 3, contain 

 numerous patches of red biotite, hornblende and augite, 

 in perfect crystal form, microcline, orthoclase, microcline- 

 microperthite, microliths of cegirine, and numerous inclu- 

 sions of zircons, apatite and magnetite, the whole cemented 

 in a coarse ground mass of quartz. Thin sections pre- 

 pared from specimens collected in an old and deserted 

 quarry on the northeast side of this island are much 

 more porphyritic. The larger crystals are always micro- 

 cline-microperthite (sp. gr. 2.60 to 2.64). One of the 

 sections has fine crystals of titanite and the quartz is in. 

 thinner films as a ground-mass or cement, otherwise the 

 minerals are of a similar character to Nos. 1, 2, 3, except 

 that no segirine was detected. Specimens were collected 

 from various outcrops along Essex avenue and Concord 

 street to a point near Coffin's beach, West Gloucester. 

 Sections, from an outcrop on the side of the road to Coffin's 

 beach, near a deserted quarry in West Gloucester, are of a 

 fine grained rock, slightly porphyritic, with an abundance 

 of biotite, perfect well twinned crystals of albite, much 

 microcline in large irregular patches, microcline-microper- 

 thite, hornblende, augite and titanite, some of the ortho- 

 clase feldspars having areas of micropegmetite. From 

 the great abundance of biotite in this rock mass it may be 

 locally called biotite-augite-syenite (sp. gr. of feldspars 

 in this rock 2.57 to 2.62). Thin sections from the augite- 

 syenite outcrop at Wheeler's point, Gloucester and extend- 

 ing to Goose Cove, Annisquam and Bay View, give the 

 microscopic structure as follows : Nos. 1, 2, Wheeler's 

 point, numerous large porphyritic crystals of microcliue- 



