56 Co Jal, Jalil OSHC OCI 
cation of Logan into the Levis, Lauzon and Sillery was recog- 
nized. In the central and southern part of the state was a great 
development of mica-schists of about the same thickness, called 
locally the Rockingham, Kearsarge and Merrimack groups. The 
well recognized Paleozoic rock of the northern parts of the 
state foot up about 16,000 feet, and were named the Cambrian 
slates, Cods group, Calciferous mica schist and the Lower 
Helderberg. 
Correlation with recognized standards.—Having established an 
order of succession, our next effort was directed to their correla- 
tion, with the generally recognized sequence elsewhere. In 
Canada the order was that of Laurentian, Labrador, Huronian 
and Cambrian; in southern New England no satisfactory deter- 
minations were available. The porphyritic gneiss naturally allied 
itself to the Augengneiss of the Laurentian of Canada and else- 
where. The Bethlehem gneiss had more affinities with the same 
group than any other; and we were fortified in our conclusions 
by the independent and unsolicited opinions of Professor J. D. 
Dana and Dr. T. Sterry Hunt. It was difficult to know where 
to place the lake gneiss, if not in the same general group. The 
Manchester and Berlin ranges rendered this reference easy 
because of their saccharoidal character. Other areas contained 
beds of magnetite, limestone and plumbago, but none of the 
Adirondack pyroxenic rocks occurred in any of them. Hence, 
the three schistose*groups would seem to correspond in general 
with the Ottawa and Grenville divisions of the Canadian Lauren- 
tian. While referring the gabbros to the Labrador system, it 
was expressly stated that they could be regarded only as an 
igneous rock, and hence not properly a stratified system. 
If these gabbros represented an igneous action occurring in the 
later Laurentian of Canada, then the schists penetrated by them 
in New Hampshire must have been equally ancient or Archean. 
Hence the origination of the term d/ontalban, representing a ter- 
rane younger than the Laurentian and older than the Huronian.". 
t This does not correspond to the signification attached to this word later by Dr. 
T. Sterry Hunt. 
