Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/657

1870.] HIND GNEISSOID SERIES OF NOVA SCOTIA. 475 an area of about 120 square miles. Around this nucleus the gold-districts of Cochran's Hill, Sherbrooke, Wine Harbor, Isaac's Harbor, and Country Harbor are arranged, also on the crown of anticlinals, which have a general easterly and westerly direction.

The profound Silurian valley shown in the map (fig. 1), between Halifax and Windsor, divides the Atlantic portion of Nova Scotia proper into two distinct geological areas, in both of which the old porphyritic Laurentian gneiss forms the axis around which Huronian and Silurian series are arranged; but, with respect to the precise limits of these formations, little is known west or east of the area shown on the plan.

From Dr. Dawson's published maps and descriptions, Mr. Poole's manuscript map of the western part of the peninsula, and the numerous rock-specimens collected by that gentleman, and placed at my disposal by the Commissioner of Mines, coupled with valuable information derived from other sources, I infer that this coarse Laurentian gneiss extends in one unbroken sheet of strata, but of variable width, a distance of ninety miles west of Windsor, and occupies a large portion of the uninhabited wilderness in that part of the Province. Much of the gneiss, schist, and mica-slate seen by Mr. Poole, and described in his Report, and illustrated by his specimens, together with the gneiss, mica-schist, and chloritic beds alluded to by Dr. Dawson, and by that geologist long ago spoken of as probably older than the Lower Silurian, are doubtless the representatives in many instances of the Huronian in the district where they occur.

In the autumn of 1868, Dr. Honeyman, then engaged on the Geological Survey of Canada, discovered on the Gulf-coast of Nova Scotia, in the Arisaig district, and near the base of the Antigonish mountains, syenites, diorites, and crystalline limestone, with serpentine. Specimens were sent to Montreal for examination ; and instructions were given by Dr. Hunt to the lapidary to prepare sections of the serpentinous rock for microscopical examination. By some mischance this was neglected, and the specimens remained unexamined, and indeed forgotten, until quite recently, as Dr. Hunt informs me, under date Feb. 3, 1870. When submitted to the microscopic test, forms resembling Eozoon canadense were distinctly seen. These may be of Laurentian age*.

In other parts of Nova Scotia the Laurentian is yet known only in the form of coarse porphyritic gneiss ; but the area it occupies is a lake and forest wilderness, frequented only by the lumberman and hunter.

The descriptions given by Sir W. E. Logan of a similar rock in the Laurentian of Canada apply exactly to the characteristic strata in Nova Scotia. "The coarse-grained granitoid and porphyritic varieties, which often form mountain masses, sometimes have, at

serpentines, now known to be of Laurentian age, by Dr. Sterry Hunt, in Massachusetts. An account of this discovery is given in the last number of the 'American Journal of Science,' Feb. 1870.
 * The existence of the Eozoon has recently been established in limestones and

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