PETROLOGICAL ABSTRACTS AND REVIEWS 479 
laccolithic intrusion are described in detail, both megascopically and 
microscopically. These include gabbro (hessose), norite (andose), 
monzonite (monsonase), and alkalic syenite (nordmarkose) in con- 
centric zonal arrangement with which are associated as dike rocks 
quartz syenite-aplite (liparase) and lamprophyres (grano-andose and 
hornblende-grano-andose). The modes of the several rocks are deter- 
mined and compared with the norm calculated from the chemical analyses. 
The several types are considered to be differentiation products 
from an original monzonitic magma. Occurring as complementary final 
products of the differentiation are the two classes of dike rocks. In the 
case of the basic dikes it is shown that magmas of similar chemical com- 
position may produce rocks of markedly different mineralogical compo- 
sition—the essexite and camptonite dikes. 
A brief general discussion follows on the broader application of the 
principles derived from the study of this peculiar aggregation of rocks, 
and the author concludes with a speculation concerning the origin of 
the alkalic magma. A. W. STICKNEY 
SOLLAS, W. J., and McKay, ALEXANDER. The Rocks of Cape 
Colville Peninsula, Auckland, New Zealand. Two vols. 
Wellington, 1905 and 1906. Pp. 289 and 215. Illustrated. 
These two volumes constitute a report relating to the Hauraki 
goldfields of the Auckland Provincial District, and mainly to Cape 
Colville Peninsula. The preliminary part of the report, of over a 
hundred pages, by Alexander McKay, government geologist of New 
Zealand, gives a general introduction to the geology of the district. 
The remainder of the first volume and the greater part of the second is 
taken up with petrographic descriptions of some four hundred thin 
sections of rocks from the Colville Peninsula; the determinations and 
petrographical descriptions by Professor Sollas, and the illustrations 
and notes as to locality, formation, etc., by Mr. McKay. There are 
also described ninety-two thin sections from other parts of New Zealand, 
including the Cheviot Hills and the east shore of Palliser Bay, 
Wellington. 
The volumes are profusely illustrated with hundreds of full-page 
halftones of thin sections, a most excellent though expensive method 
of assisting a reader to obtain an idea of the individual rock specimens. 
Unfortunately many of the halftones are not so sharp as they might be, 
but the work, on the whole, is the most elaborate catalogue of rock 
slides yet attempted. ALBERT JOHANNSEN 
