1895. | NEW YORK ACADEMY OF SCIENCES. 195 
has recently been worked out in Diy. 16 of the St. John group.* 
Mr. Walcott + includes the Etcheminian, which contains a few 
fossils, none satisfactory as determining its relations, in the 
the Cambrian period. In this case it would become a question 
as to how much value can be assigned to the unconformity be- 
tween the Etcheminian and the volcanic rocks beneath, and 
whether the latter might not also be included in the Lower Cam- 
brian. Between the Laurentian and all the later rocks there ap- 
pears to be a great break, if one may judge from lithologic 
characters and the lack of conformity in dip in many places. 
Satisfactory conglomerates are, as might be expected, lacking 
at the base of the volcanic series. In some observed cases the 
rock nearest the contact is a breccia (volcanic); but it is not 
known whether any of these contacts are not obscured by 
thrust-planes. That the St. John group is separated from the 
Laurentian by a great break there is good evidence; a conglo- 
merate at its base has been observed to contain pebbles of the 
Laurentian rocks. 
CLASSIFICATION. 
It has been thought most convenient in the present paper to 
discuss the igneous rocks of the Coldbrook, Coastal and Etche- 
minian together, dividing them according to physical charac- 
ters, and ‘subsequently to take up the Kingston rocks as meta- 
morphosed phases of these. It is found that the division into 
Acid and Basic Effusives, used by Dr. Williams for the igneous 
rocks of South Mountain, is a very convenient one to employ 
here, the intermediate types being but poorly represented. The 
dykes, clearly recognizable as such, are discussed separately, 
as is also an occurrence of soda granite which has been referred 
to the Huronian in the Survey Reports. In order to give some 
clear understanding of the character of the rocks included under 
these divisions they have been placed in groups which in the 
sections studied are fairly distinct one from another. It has 
not been possible to make any well founded generalizations as 
to the distinctness of these groups in point of time, still less as 
to their succession. The arrangement is as follows: 
EFFUSIVE Rocks. 
A.—Acid Effusives. : 
l. Quartz Porphyry. Compact, quartzose, full of pheno- 
crysts. 
* These Transactious. Vol. xiv., April, 1895. 
+ Correlation Papers-Cambrian, U.S. G.S. Bull., 81. 
t Trans. Roy. Soc. Can., 1889, Sec. 4, p. 139. 
