422 NATURAL SCIENCE [December 
to be a sketch, and granite is selected as the deep-seated type, fol- 
lowed by four lavas. Augite or soda-augite, as well as hornblende 
and biotite, should, we think, have been mentioned among the com- 
mon constituents of rhyolite (p. 122) and trachyte (p. 124). We do 
not quite gather the meaning of the description of andesites “as gener- 
ally dark, and mostly fine-grained rocks, with a restricted amount of 
glassy base, but larger than in the trachytes.” 
On p. 127 we commence the study of North American volcanoes, 
and it is interestingly pointed out (p. 153) that the two ends of the 
great western line are highly active, while there is a “middle region 
of extinct or, perhaps, in part, dormant volcanoes, extending from 
central Mexico through the western part of the United States and 
far into Canada.” 
Considering the enormous area to be covered, no one geologist can 
be expected to have an intimate acquaintance with North American 
volcanoes ; and hence the description of those in Central America and 
Mexico is necessarily a compilation from works already published. 
So little is known of this district, however, that we are glad to be put 
in touch with the amazing history of Izalco, the growth of which, from 
nothingness to a height of 1500 feet, was witnessed by the curé of 
Sonsonate during his quiet country life, or the catastrophic explosion 
of Conseguina in 1835, which seems to have been connected with 
earthquakes that carried ruin into Chile. Among recent accounts 
—still far too few—we have those of Prof. Heilprin’s ascents in 
Mexico. There seems some contradiction, however, between p. 178, 
where we are promised mountaineering excitements on Ixtaccihuatl, 
and the mere comparison with Popocatepetl on p. 183. 
A country that possesses the denuded necks near Mount Taylor 
(Pl. 6, fig. B), and the exquisitely preserved Ice Spring craters of 
Utah (PI. 7), is truly a paradise for the student; but the distances 
from point to point must still remain obstacles to research. ‘The cone 
near Lassen’s Peak, described by Diller, is of admirable freshness, and 
may have been active in the present century. Hence there are 
further volcanic possibilities in store for observers within the 
limits of the United States. 
On p. 234 we gain a conception of the huge chain of peaks, still 
awaiting detailed enquiry, that runs north from San Francisco into 
Washington. These seem to result from Tertiary eruptions, and are 
not unworthy companions of the Andes, which are more familiar to 
us, owing to the pre-eminence of certain of their summits. The photo- 
graph of Mount Rainier (Pl. 14) may be cited, among the beautiful 
series of illustrations that adorns Prof. Russell’s book. 
The account of the Columbia, lava (p. 250) will interest students 
of fissure-eruptions. Prof. Russell clearly points out that the enor- 
mous area, 200,000 to 250,000 square miles, is not buried in one 
vast flow; “the lava sheets overlap and supplement one another so 
as to form a continuous and highly compound system.” Individual 
flows have, however, been traced on cafion-walls for a score or more 
of miles. 
When we reach Alaska, we welcome the photographs of peaks and 
islands on Plates 15 and 16, and feel more than ever grateful for the 
records that Prof. Russell has brought together in the American 
