Page:Picturesque Dunedin.djvu/89

Rh Waihola Railway Station, 26 miles away on the main South line, where, on the borders of the lake, and well exposed in the cutting, we find a deposit consisting of moderately coarse beds of sand and silt, containing large angular blocks, and dipping to the south-east at somewhat low angles up to 30 deg. Within the township these sands have been invaded by volcanic rocks, which appear as massive dykes from four to fifteen feet across, considerably altering and indurating the sands and clays, and within the upper township breaking through the lower beds of the coarser upper part of the formation. This deposit, which is supposed to be of glacial origin, extends from Waihola in a north-easterly direction to Brighton, a distance of about twelve miles, and is in its upper part, composed of exceedingly angular material, the blocks in places being from five to ten and even twelve feet in diameter, loosely compacted together, the fragments being often surrounded with fine material. Passing the Taieri River, which drains a considerable area of the north-eastern portion of Otago, and at the mouth of which, as also further down the coast, there are valuable deposits of manganese; we skirt the Taieri Plain, leaving an outline of the Green Island coalfield on our right, where the basaltic peak of Saddle Hill caps the coal measures, and plunge into the bowels of the earth at the Chain Hill tunnel, which is excavated through a formation of fine-grained laminated mica-schists or phyllites. These form a ridge of hills which run out to the sea-coast at Brighton, and soon after leaving the heavy cutting, we are on the borders of the coal measures, which lie unconformably on the schists, and deserve more than a passing notice. The rocks here consist of sandstones, shales and clays, with seams of coal; these dip in an easterly direction at one in ten under the Caversham sandstone, which is a tertiary marine formation, and is again overlaid by the volcanic rocks of the Dunedin basin. The coal-seams extend along the western boundary in a line running from the mouth of the Otakia Creek for about nine miles to the valley of the Water of Leith. Starting at Brighton, the south-western limit of the field, we find, not far above sea level, a seam of coal 14 feet in thickness, dipping to the east at six deg., and worked on a small scale by an adit. The natural cover of the seam has been in places denuded, and a recent