1 889]. Mineralogy mid Petrography. 157 
grained varieties of the rock often appear as if included in 
lighter colored coarser grained kinds, the color of the two rocks 
depending upon the percentages of augite in them. The dense 
varietiesoften show a fluidal structure in the arrangement of little 
microlites of augite, and sometimes possess these in dendritic 
groups. Rutile is noted as an alteration product of sphene, 
and several unknown minerals are briefly described. — Inan Eng- 
lish summary at the end of his book^ Reusch gives a description 
of the remarkable geological region of Norway where erup- 
tive, sedimentary, vein and dyke rocks have had developed in 
them by the action of great pressure, a schistisity which was 
attended by chemical change in the original constituents of 
he rock masses. Through processes carefuljy described the 
author shows that granite may originate from clastic rocks and 
afterwards be intruded as an eruptive into other eruptive and 
clastic rocks in the form of dykes. Gneiss veins are said to be 
common in the region, and schistose gabbro, diabases and 
other basic rocks occur in great quantity. The book contains 
three colored maps and two hundred-and-five wood-cuts of 
geological sections and sketches of thin section of rocks. From 
his observations, Reusch draws some important conclusions 
which will probably explain many of the difficulties 
met with in solving the problems of the origin of crystalline 
schists. — A hornblende-peridotite' from a hill at the south 
foot of Kilimandjaro in E. Africa is an allotriomorphic granu- 
lar aggregate of grass-green hornblende, salmon colored hyper- 
sthene and colorless olivine. The hornblende and olivine 
include rows of opaque rod-like bodies. The hypersthene is 
pleochroic as follows: «=salmon-red: /^ = pale yellow ; <: = sea- 
green. Pleonast and magnetite are among the other constitu- 
ents.— A few small isolated patches of a green rock occurring 
just north of Aberdaron in North Wales, and colored as 
serpentine on the survey maps of Wales are regarded by 
Elsden' as serpentinized diabases. Unaltered diabases, horn- 
blende-gabbros, and porphyrites from the same region are also 
briefly described by the author.— Mr. Wethered* has discovered 
well outlined quartz crystals in the insoluble residues of the 
Carboniferous limestones at Clifton, England, that have result- 
ed by the enlargement of fragmental quartz grains by the 
deposition of silica derived from organic sources.— -In the 
^ ^°"sX5f '°^" °^ Karmoen med. omgivelser geologisk beskrevne. Kristiania. 
'"^t^h: Geol. Magazine, May. 1888. p. 257. 
'Geol. Magazine, 1888. p. 303 
Quart. Jour. Geol. Soc. May, 1888. p. 186. 
