210 TRANSACTIONS OF THE [apr. 15, 
neath Paleozoic strata. Whether they are considered as the 
lowest member of the Palzeozoic series or the uppermost one of 
the pre-Cambrian rocks would seem to depend chiefly on what 
may be taken as the base of the Paleozoic. In New Brunswick 
it is rather more than elsewhere convenient to consider them 
as at all events pre-Cambrian, and to take the very persistent 
coarse grey sandstone at the base of the St. John group as the 
dividing line. This would leave both the volcanic series and the 
Etcheminian among the pre-Cambrian rocks. Nevertheless their 
age is probably not greatly different from the so-called Cambrian 
effusives lying southwest of them. 
THE DYKES. . 
In all the rocks referred to the “ Laurentian,” we find a great 
abundance of dykes. In the later rocks they are few in nnm- 
ber. In the volcanic series they are, naturally, not easy to re- 
cognize; a number of supposed sills are known, but of small 
dykes crossing the bedding of the rocks very few. The Etche- 
minian contains one certain dyke, and probably others. In the 
St. John Group one dyke is reported from near the city, but I 
have not seen specimens of it. Though none have been met in 
the Devonian slates, a few occur in the Sub-carboniferous.* 
The vast majority of the dykes in Laurentian rocks, as well as 
the dyke and sill in the Etcheminian, are ordinary diabase, more 
or less altered and often porphyritic. With these occur several 
dykes which can be grouped under Prof. Rosenbusch’s term of 
Diorite-porphyrite, though they border on camptonite. The 
Sub-Carboniferous dykes, with one or two occurring in older 
rocks, are augite-porphyrite. Some dyke rocks appearing to be 
of other types are known, but are all so altered as to be unrec- 
ognizable. 
As arule no general trend is to be distinguished in the direc- 
tion of the diabase dykes. An exception is seen at Pleasant 
Point, where the granite is seamed with dykes, most of which 
are perfectly straight and parallel, with a north-west and, south- 
east direction, parallel to the great cross-fault of the Short 
Reach. 
DIORITE-PORPHYRITE. PI. XIV. Figs. 1 and 2. 
Under this name may be grouped a number of dykes varying 
a good deal in character, but all distinguished by a groundmass 
consisting of sharply idiomorphic hornblendes, lath-shaped feld- 
* These notes apply merely to the neighborhood of St. John. 
