1004 The American Naturalist. [November, 
their chemical composition, but that types with the same general 
chemical relationships possess the same general mineralogical charac- 
ter. The author also gives his views on the relationships existing 
between the various rock types, as based on their calcium and alkali 
ratios, and, while not so stating it, he shows that the emanations from 
an eruptive center are consanguinous. 
Norites in the Eastern United States.—Along a shear zone in 
the norite of Avalanch Lake in the Adirondacks, Kemp* finds what 
he believes to be a schistose phase of the rock in which several new 
minerals have been developed. The massive norite consists chiefly of 
plagioclase, with a little hornblende, enstatite and magnetite. In the 
schistose rock, which is much more basic than the norite, are broken 
pieces of plagioclase, shreds of hypersthene, grains of green monoclinic 
pyroxene, pink garnet, greenish-brown hornblende, biotite and magne- 
tite, of which both the monoclinic pyroxene and the garnet are sup- 
posed to have been produced from the hypersthene and the plagioclase 
of the original norite. The schist resembles an eclogite. The same 
writer’ records the discovery óf a new occurrence of norite or of E. 
thene gabbro at Artsdalen's quarry in Bucks County, Pa. It is ass 
ciated with a limestone which is the matrix of a large number of 
metamorphic minerals. It is thought that this limestone may be a 
block brought from below by the eruptive. The region surrounding 
thé quarry is underlain by pre-Cambrian rocks, but it is almost with- 
out exposures. The occurrence of norite here is interesting as afford- 
ing a link connecting the otherwise separated Baltimore and Cortland 
areas of basic eruptives. 
The Ottrelite Conglomerate of Vermont.— Reference has 
already been made in these notes to the discovery of an ottrelite con- 
glomerate in the Green Mountains of Vermont. Whittle? has now 
given us in more detail the description of its occurrence, and adds to 
this many items of interest concerning the dynamic schists associated 
with it. Among other things connected with the minerals of the con- 
glomerate he mentions the secondary enlargement of clastic tourmaline 
grains and describes the alteration of microcline pebbles into quartz, 
sericite, biotite and albite. In one microcline there are many inclu- 
sions of limonite and rhombs of siderite. As the sericite grows it clears 
ê Amer. Journ. Sci., Aug., 1892, p. 109. 
T Trans. N. Y. Acad. Sci., xii, p. 71. 
8 AMERICAN NATURALIST, April, 1893, p. 382. 
? Bull. Geol. Soc. Amer., iv, p. 147 
