98 REGINALD A. DALY 
BOWEN’S EXPLANATION OF THE ALKALINE RocKs—Continued 
Rapid transitions between phases of differentiated injections 
Origin of quartz diabase 
Gas-controlled differentiation in the liquid phase 
Question of liquid immiscibility 
Failure of sufficient allowance for magmatic assimilation 
Differentiation a reversible process 
Hybrid rock not the normal result of assimilation 
Meaning of chilled contacts of batholiths 
Loci of magmatic assimilation 
Bowen’s special suggestions as to origin of alkaline types 
Assumed desilication by the settling-out of quartz crystals 
Origin of basanite 
Absence of foyaitic types in most batholiths and stocks 
Absence of quartz-bearing lavas in many basalt-trachyte-phonolite 
volcanoes 
Eruptive sequence 
Comparison of basalt and femic, feldspathoid-bearing types 
Admission of some assimilation by magmas 
Meaning of melilite rocks 
Résumé 
GENERAL CONCLUSION 
INTRODUCTION 
The eruptive sequence in the compact and quite isolated igneous 
complex at Ascutney Mountain, Vermont, opens with gabbro and 
closes with dike rocks, including its chemical equivalent, diabase. 
The gabbro seems locally to merge into a type intermediate between 
essexite and a basic diorite. That body is cut by dikes of a mafic 
rock which shares the characteristics of monzonite and ideal 
essexite.t Intruding the gabbro, “‘diorite,”’ and essexitic monzonite 
are several stocks or thick dikes of alkali-rich syenites, themselves 
cut by a stock of alkaline granite. Still younger are the diabase 
dikes. 
The study of Ascutney Mountain, begun in 1893, introduced 
the writer to the problem of the so-called alkaline rocks. There he 
first became skeptical of the dogma that the alkali-rich magmas 
have originated independently of the subalkaline (lime-alkali) 
«The relation between this microperthite-orthoclase-plagioclase rock and the 
gabbro-‘‘diorite’’ body, described in Bull. 209, U.S. Geol. Surv., 1903, was proved in 
IQ16. 
