s 
T. S. Hunt on Lithology.. 255 
unlike conditions that one may regard it as indigenous, and the 
other, with equal reason, may set it down as intrusive. It is evi- 
dent then that to the lithologist, who examines rocks without 
reference to their geological relations, the question of the exotic 
or indigenous character of a given rock is, in most cases, one 
altogether foreign; and one which can frequently be decided 
only by the geologist in the field. Hence, although generally 
made a fundamental distinction in classification, it will be disre- 
garded in the following sketch of the nomenclature of crystal- 
ine rocks, 
_ Imay here allude to a fact which I have already noticed, and 
tried to explain, (this Journal, [2], xxxi, 414, and xxxvi, 220, 
note,) that throughout the great metamorphic belt which consti- 
tutes the Appalachian chain, exotic rocks are comparatively rare, 
(at least in New England and Canada); but abound, on the con- 
trary, among the unaltered strata on either side. Illustrations of 
this are seen in the valley of Lake Champlain, and in its north- 
ward continuation toward Montreal, in those of the Hudson and 
Connecticut, and in the northeastward continuation of the latter 
valley by Lake Memphramagog to the Bay of Chaleurs, which 
is marked throughout by intrusive granites. In accordance with 
the reasons already assigned for this distribution of exotic rocks 
it is probable that a similar condition of things will be found to 
exist in other regions; and that eruptive rocks will, as a general 
rule, be found among unaltered, rather than among metamorphic 
strata. It is of course possible that a crystallization of the sed- 
iments may in some cases take place subsequent to the eruption 
of foreign rocks into their midst. The rarity of intrusive rocks 
among crystalline strata, not less than the unaltered condition of 
Sediments which are traversed by abundant intrusive masses, 18 
4strong proof of the fallacy of the still generally received no- 
tion which connects metamorphism with the contiguity of erup- 
tive rocks, 
