374 
HYPOGENE ROCKS. 
[Ch. XXVI. 
district, the lowest of these will be converted into hornblende- 
schist, while the uppermost may continue in the condition of 
clay-slate. 
The term 'Hypogene ' proposed for Primary. — If our readers 
have followed us in the train of reasoning explained in this and 
the preceding chapter, they must already be convinced that 
the popular nomenclature of Geology, in reference to the so 
called ' primary ' rocks, is not only imperfect, but in a great 
degree founded on a false theory ; inasmuch as some granites 
and granitic schists are of origin posterior to many secondary 
rocks. In other words, some primary formations can already 
be shown to be newer than many secondary groups — a mani- 
fest contradiction in terms. 
Yet granite and gneiss, and the families of stratified and 
unstratified rocks connected with each, belong to one great 
natural division of mineral masses, having certain characters in 
common, and it is therefore convenient that the class to which 
they belong should receive some common name — a name which 
must not be of chronological import, and must express, on the 
one hand, some peculiarity equally attributable to granite and 
gneiss (to the plutonic as well as the altered rocks), and which, 
on the other, must have reference to characters in which those 
rocks differ both from the volcanic and from the unaltered 
sedimentary strata. We propose the term * hypogene ' for this 
purpose, derived from vvo, subter, and ytvopoai, nascor, a word 
implying the theory that granite and gneiss are both nether- 
formed rocks, or rocks which have not assumed their present 
form and structure at the surface. It is true that gneiss and 
all stratified rocks must have been deposited originally at the 
surface, or on that part of the surface of the globe which is 
covered by water j but according to the views explained in this 
and the foregoing chapter, they could never have acquired 
their crystalline texture, unless acted upon by heat under pres- 
sure in those regions, and under those circumstances where 
the plutonic rocks are generated. 
The term ' Metamorphic ' proposed for stratified primary . — 
