210 REPORT ON CORRELATION 
Whether these intrusions of gabbro antedate those of the granite 
cannot be determined with certainty, as the two sets of occurrences 
are- not found in contact. 
In Logan’s original examination of the southern portion of the 
area he used the designation “Hastings series” for the less altered 
portion of the series, and the term ‘‘Grenville” for the more ‘highly 
altered portion. He expressed the opinion, however, at the time, 
that the Hastings series in all probability represented the Grenville 
series in a less highly altered form. 
V. RESUME OF THE GEOLOGY OF THE “ORIGINAL LAUREN- 
TAIN AREA” AND ITS EASTERLY CONTINUATION IN THE 
DISTRICT TO THE NORTH OF THE ISLAND OF MONTREAL 
It has been thought well to make reference here to the ‘ Original 
Laurentian area” and to its easterly continuation to the north of 
the island of Montreal. The committee did not examine these 
districts, but the former was studied by Sir William Logan in the 
early years of the Canadian Survey, a map of it having been published 
in the atlas accompanying the report of the survey for 1863, while 
the latter district was studied by F. D. Adams, his report and map 
of it appearing in 1896. As the studies in these districts have played 
an important part in shaping the nomenclature adopted in the case 
of the pre-Cambrian rocks of eastern America, the committee 
requested Dr. Adams to prepare the following brief description of 
them. 
The “Original Laurentian area” of Logan lies in the province of 
Quebec, on the north shore of the Ottawa River, between the city 
of Montreal and the city of Ottawa, and takes its name from the 
township of Grenville and the village of that name, which lie within 
it. The second area mentioned forms the continuation of this 
‘Original Laurentian area” to the east, and embraces the district 
about St. Jerome and eastward nearly as far as the St. Maurice River. 
There is every reason to believe that the area embraced by these 
two districts represents the continuation of the pre-Cambrian series 
studied by the committee in eastern Ontario, seeing that both occupy 
precisely the same relative position along the southern margin of 
the protaxis and that rocks similar to them in petrographical char- 
