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. 133) 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 lzalco, the growth of which, from 

 nothingness to a height of 1500 feet, was witnessed by the cure of 

 Sonsonate during his quiet country life, or the catastrophic explosion 

 of Consesuina in 1835, which seems to have been connected with 

 earthquakes that carried ruin into < 'bile. 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 (PL 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 overlay) and supplement one another so 

 as to form a continuous and highly compound system." Individual 

 flows have, however, been traced on canon-walls for a score or more 

 of miles. 



When we reach Alaska, we welcome the photographs of peaks and 

 islands on Plates 15 and 10, and feci more than ever grateful for the 

 records that Prof. Russell has brought together in the American 



