1885.] Mineralogy and Petrography. 499 
another, whatever be the changes of chemical or mineral compo- 
sition or of structure, within certain limits, form a species; but 
what these limits are is not stated. A diorite derived by para- 
morphosis from a gabbro must be called a gabbro, Even quartz 
which might have replaced a basalt would have to be called 
basalt, strange as this would seem, unless these “ certain limits ” 
be defined. Wadsworth's classification seems to be, after all, 
mainly a chemical one in which the rocks of approximately the 
same composition, but differing in their constituents, structure or 
degree of alteration are arranged under the principal species as 
varieties. 
Chapter second commences the systematic treatment of rock 
classes, starting with the most basic. The suggestion of Reyer, 
to consider the meteorites as eruptive rocks more basic than any 
normally found near the earth’s surface, is wisely followed. Spe- 
cies 1, Siderolite, is made to include all masses of iron, either 
native or in its secondary state as magnetite, hematite, etc., which 
are not of chemical or secondary origin. This species is of course 
principally represented by meteoric iron. Species 11, Pallasite, 
includes such original, eruptive, celestial or terrestrial rocks as 
contain a large amount of native or oxidized iron inclosing other 
minerals. Twenty-two meteoric pallasites are mentione 
terrestrial variety of pallasite is described the so-called “ cumber- 
landite ” from Rhode Island, an apparently eruptive mass of mag- 
netite full of crystals of olivine, feldspar, etc. Analogous to this 
is Sjoren’s “ magnetite-olivinite” from Taberg, in Sweden. 
Chapter third deals with Species 111, Peridotite. This name 
was given by Rosenbusch to massive rocks composed essentially 
of olivine together with various pyroxenic minerals. The author 
classifies these as follows : 
Variety 1. Dunite = olivine + picotite. 
“ 2, Saxonite = olivine + enstatite. 
“ 3. Lherzolite = olivine + enstatite + diallage. 
“« 4, Buchnerite = olivine + enstatite + augite. 
“ 5, Eulysite = olivine + diallage (= “ Wehrlite gf 
« 6. Lione = olivine -+ augite. 
Serpentine is derived by alteration from all of these. 
Eulysite is a name that was originally applied to a rock very 
rich in garnet, and it is difficult to see why it is preferred to the 
German term wehrlite, used for olivine-diallage rocks. Forty 
meteoric peridotites are enumerated, following which is a section 
devoted to the origin and character of meteorites in general. The 
“chondri” are regarded as spherules due to crystallization, and 
the meteorites themselves as having probably been thrown off by 
the sun. Then succeeds the description of many terrestrial peri- 
dotites and serpentines, with general remarks on their character 
and origin. Considerable space is devoted to the relations be- 
