206 REVIEWS. 











of matter were left in a state of fusion, which find their outlets int 
existing volcanoes. 
sA 
S 
h in ma and volcanic Se e the se fem rocks are 
first or aa “gees. then in cessive, though not invariable, 
sequence, the Andesitic, Trachytic, Terpen and Basaltic lavas. 
volcanoes are divided into two classes, those which still continue to 
i ive 
tions,” from which the author EASES they take their rise, and t 
the ejected rocks. 
Lassen’s Peak in Northern California belongs to the latter class. 
on 
reams succeed in arti tig sloping tables; rhyolite composes © 
resent summit to the dept fifteen hundred feet; and, lastly, 
separated, are inferior rents to Pr north which have thrown out 
apparently very recent origin. RE 
Thus the periodical nad rigs place in such larger active j 
canoes, AAAA in the order of their succession with those 
by the o th more massive eru 
pti 
Active volcanoe erefore, yi dhait as belonging to the p 
pylitic, eros shes ha rhyolitic, or basaltic epoc hs, or as e 
ges of 0 
one of these and passing through several successive sta 
ment. ee 
Thus Lassen’s Peak has reproduced, during its successive Ch hanges: 
structural features of existing Andesitic, trachytic, rhyolitic, and 
volcanoes, and also the order of succession which is observ 
sive eruptions of former periods. The author, however, oa 
that, in some instances, the order of succession is part vite 
in the island of St. Paul in the Indian Ocean, where the rhyo be 
are overlaid by basalt, and this again by rhyolitic and basaltic 
succession n. a en 
Following upon this is an highly interesting discussion E age 
composition, correlations of age and texture, correlations 
composition, the geographical distribution, and t the origin of 
k ; 
The extrusion of the lava is accounted for by the expansie nd 
consequent upon the changes of the denser rocks around the w 
of the cracks or orifices, from a solid or highly viscous — 
aqueous fusion. 
Granite and Syenite are regarded as the product of very ? 
sive eruptions, and as of wholly volcanic origin. 
