Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/256

154 3. Bole — an indurated red ferruginous ochre, less compact than that of Slievananee, Thickness 2 ft. passing into and alternating with

4. Yellow Ochre, Thickness 3 ft. which graduates into

5. Blue Lithomarge. Base not seen, but thickness proved to 29 ft. 6 in.

The several masses in the above section, as, indeed, in others, exhibit a pseudo-stratified arrangement, here dipping at an angle of 34°, E. 50° N. magnetic. The whole mass has been bored to a depth of 45 feet, which gives a minimum thickness for the iron ore, ochres, and lithomarge of 37-1/3 feet.

3. Enumeration of localities. — Passing east from Slievananee, the iron-beds are worked from the face of the basaltic escarpment overhanging Milltown, Red Bay, at the entrance to Glenariff Glen ; the beds dip west about 5°, and are about 200 feet above the upper limit of the White Limestone. Further to the east, the iron-band has been traced to near Garron Point.

Two miles to the west of Carnlough, the ferruginous series is seen at a height of 600 feet above the sea -level, dipping at an angle of about 40° east (magnetic). The matrix of the pisolitic ore, 22 inches in thickness, is of a bright vermilion-red colour, becoming browner as it passes downward ; it then passes into a friable yellowish ochre, four and a half feet thick, which, in its turn, graduates into a blue lithomarge, 35 feet thick. Overlying the pisolitic ore is a semiprismatic basalt, the columns of which are perpendicular, and consequently include, with the underlying strata, an angle of 50°.

Other outcrops are worked at Ballyvaddy and Tully, near Glenarm, andat Anteville, Kilwaughter (3 mines), and Shane's Hill (2 mines), near Larne.

4. Deductions from the several sections. — We deduce from the foregoing sections the gradual passage of the underlying basalt into a variegated lithomarge of an average thickness of 30 feet, graduating insensibly into the overlying red or yellow ochre or bole, 5 to 6 feet thick, which passes into, and is surmounted by, a pisolitic iron-ore of an average thickness of two feet. The spheroids of iron-ore increase in number and size towards the upper part, and not unfrequently constitute that portion of the bed. The line of junction between the iron-band and the overlying basalt (which is usually more or less columnar), is well defined, and in a few instances exhibits decided unconformability.

Though a band of iron-ore can be traced with some certainty over a considerable area, yet it is by no means proved that the ore in the various sections, many of which are several miles distant from each other, represents portions of one sheet extending uniformly throughout the basalt. To determine this, point will require a laborious survey of the country, chiefly because of the numerous faults — a task too gigantic for us to perform. Still we are justified, from the identity of the phenomena in the many sections examined, in assuming that in the midst of the basaltic rocks there is a continuous band of iron-ore.

Only in two instances have we been able to refer the iron-band