516 The American Naturalist. [June, 
mens; perlitic parting is occasionally detected in them; amygdaloidal 
phases are not uncommon, while taxitic and trichytic structures are 
frequently met with. The original components of many of the South 
Mountain rocks have entirely disappeared and in their place are now 
found only quartz, epidete, magnetite and leucoxene. These minerals 
are evidently secondary and yet in some specimens they are associated 
in micropoicilitie intergrowths, thus indicating to the author the 
secondary origin of this structure in the present instance. The 
spherelites in the rocks under consideration are often imbedded 
in a base that was formerly a glass, though it is now a holocrys- 
talline quartz—feldspar mosaic, which must necessarily be of the 
nature of a devitrification substance, since the mosaic is crossed by 
delicate perlitic partings. The rocks of the region are thus compara- 
ble with the lava flows of more recent age. Some of them were obsid- 
ian, others were lithoidal rhyolites and others holocrystalline rhyolites. 
The structure of the obsidians is now microcrystalline in consequence 
of the alteration or devitrification processes to which they have been 
subjected. ey are now felsites or microgranites, but their micro- 
granitic structure is not original. It is the result of devitrification. The 
author would therefor not call the rock a microgranite, nor an obsidian, 
but would designate it as an apobsidian or an aporhyolite, indicating 
that it was once an obsidian which has become devitrified—the prepo- 
sition signifying that the rock to which it is prefixed has undergone 
alteration of a specific nature. 
Another Occurrence of Websterite.—Another occurrence of 
the basic rock websterite is reported by Harker’ from Fobello, Lom- 
bardy, Italy. The rock is a dark aggregate of black diallage mould- 
ing smaller grains of hypersthene. In thin section the diallage is cot- 
orless. An eclogite from Port Tana, Norway, consists of garnets 
holding inclusions of ecyanite, omphacite and zircon, imbedded 1m 
a groundmass composed chiefly of colorless omphacite and quartz, in 
which lie phenocrysts of idiomorphic enstatite. A garnet amphibo- 
lite from Sutherland, England, a quartz diorite from Viti Leon, Fig), 
and a uralitized gabbro from Ena, Tonga Islands, are also described 
by the same author. 
_Petrographical News.—The nickel ores of Sudbury, Ontario, 
like those of Norway and Sweden, are associated with gabbro aP 
norite, along their contact with other rocks. The ores are supposed by 
"Geol. Magazine, VIII, 1891, p. 1. 
