992 General Notes. [ October, 
in well defined crystals, and “ xenomorphous” when it merely 
fills the spaces left between the plagioclase crystals, as is common 
in rocks of the diabase type. A compact brown hornblende is a 
common constituent and presents the most interesting relations 
to the augite. These are described at length and admirably illus- 
trated in a colored plate. This hornblende which very frequently 
makes up the outer portion of a pyroxene crystal, is regarded as 
in no way of secondary origin, but as an original crystallization 
due either to changes in chemical composition or physical condi- 
tions in the magma. The following analyses of the two minerals 
illustrate instructive chemical differences: - 
Augite. Flornblende. 
oS ee ee 44.22 36.91 
Beis ks ewes see 10.49 16.30 
BR Vics scans Dee peteodabea ks see a aa 11.98 5.28 
Te a a be BE ESE E A ERR e R y 5-77 52.27 
< DE becuse aed Oe ty erates Gases esees re 7.02 8.83 
Ga. ees T caceen ce ¥Oree e¥iein Fire sys 22.54 16.91 
102.02 96.50 
The hornblende contains 3.5 per cent of alkalies. 
The nepheline Dr. Rohrbach was unable to discover in any 
-specimens of teschnite from either Moravia, Caucasus or Portu- 
gal. He thinks that what has thus far been considered to belong 
to this species is in reality apatite, and would hence strike tesch- 
nite from its place in Rosenbusch’s system. 
[Even in case Dr. Rohrbach’s results regarding the presence of 
nepheline in the specimens examined by him are entirely correct, 
no account has been taken ọf the dykes of ancient plagio- 
- clase rocks occurring in the Silurian limestone near Montreal, in 
Canada, which, according.to Drs. Hawes and Harrington, are un- 
doubtedly rich in nepheline. This mineral is often present in 
large sharply-defined hexagonal crystals closely resembling those 
so characteristic of the Katzenbuckel “ nephelinite.” —G. H- W.]. 
METAMORPHOSIS OF GABBRO.—The widespread origin of horn- 
blendic schists by the uralitic alteration of massive pyroxene 
rocks receives additional evidence in its favor wherever the atten- 
tion of geologists is especially directed to it. The observations 
of Lehmann in Saxony, Reusch in Norway, Phillips in Bagreg 
Becke.in Austria, Streng and Irving in the region about 
Superior in the U. S., all indicate the great geological eri 
of molecular changes i in prodocing amphibole schists from pyrox- 
~ ene eruptive rocks, The studies of Kloos'in the Black Forest 
point to a like relation between the gabbros and diorites of Ehrs- 
berg. Mr. Frederick H. Hatch, of London, has contributed a 
similar investigation of the gabbro occurring at ’Wildschénan in the 
: “coast eri 11, Beil. Bd. 
