27 
and the chemical analysis show that the batholitic rocks and 
those of the superincumbent volcanic series are so nearly 
related that it must be assumed, according to commonly accep- 
ted hypotheses, that both kinds of rocks have originated from 
one parent magma and belong to one cycle of igneous activity. 
For this reason the rocks of the batholites are here referred to 
the same geological period as the volcanic series or in other 
words, they are supposed to be of Devonian age (compare Table, 
p 9). 
The question whether or not the process of intrusion of 
the batholites was contemporaneous with the superficial igneous 
outbursts will be considered more fully below (see Chapter VI). 
It will be shown that while the study of the contact relations 
is insufficient to settle the question, certain observed features 
of the abyssal rocks themselves apparently indicate that there 
has been at least a partial contemporaneity between both phases 
of the igneous activity. 
