1897.] Petrography. 521 
as a spherulitic glass with the composition indicated above. Explo- 
sions of steam took place before the glass had completely cooled, form- 
ing a breccia of mud, sand, solidified lava, partially solid glass. At 
one place this mixture broke through the trap sheet forming a mud 
volcano. A large number of handsome plates illustrate the descrip- 
tions. 
A Keratophyre Dyke near New Haven.—Hovey’ declares 
that a keratophyre dyke cuts the Triassic sandstones near New Haven, 
Conn. It is one of seven dykes, the remaining six being diabases. The 
keratophyre contains two sets of feldspar phenocrysts. One set con- 
sists of large crystals of albite and the other of acicular crystals of 
anorthoclase. The matrix in which these lie looks like a devitrified 
glass. Analysis gave: 
SiO, TiO, Al,O, Fe,O, FeO Mno MgO CaO Na,O K,O Ign Total 
60.13 tr 20.47 1.04 .72 tr 1.15 2.59 9.60 1.06 3.44—100.20 
The loss on ignition is largely CO,. Thisisthe first acid dyke reported 
in the Triassic sandstone of the Atlantic border. 
The Gabbros near Ronsperg, Bohemia.—A group of rocks 
belonging to the gabbro family is described by Martin‘ from the vicin- 
ity of Ronsperg, Bohemia. Gabbros and olivine-gabbros are the prin- 
cipal rock types met with. They constitute intrusive layers between 
pegmatite and amphibolite. Near the amphibolite the gabbros grade 
into quartz diorites. At Hoslau a smaragdite gabbro occurs in scattered 
ledges, and between these, near a granite with which the basic rock 
may be in contact, are ledgesof norite. Wehrlite ledges are also found 
in the same vicinity. These are believed by the author to be basic in- 
clusions in the intrusive rock. The olivine of the olivine-gabbro is 
often surrounded by arim consisting of orthorhombic pyroxene, brown, 
green and colorless hornblende, and spinel, all of which are thought to 
be secondary. Diallage and orthorhombic pyroxenes, and this mineral 
and olivine, are often in parallel growths when all are original. The 
smaragdite-gabbro is much decomposed, its diallage having been 
changed to smaragdite and its plagioclase to cloudy grains filled with 
zoisite and clinochlor. 
Exotic Blocks in the Eocene Schists of the Alps.—The 
Eocene schists of the Alps have long been known to include exotic 
* Amer. Jour. Sci., III, 1897, p. 287. 
t Min u. Petrog. Mitth., XVI, 1896, p. 105. 
