Page:Picturesque Dunedin.djvu/91

Rh Caversham station, we enter a tunnel which is 950 yards in length, and excavated entirely in the sandstone, here remarkably compact, containing only five or six cracks in its total length. It is a soft calcareous sandstone, generally bluish-grey, or yellow, and unfortunately not well adapted for building purposes; had it not been for a protecting cover of basalt, no doubt erosion and weathering would have obviated any necessity for taking the railway below ground. Before arriving at Dunedin we skirt the hills on our left, leaving the South Dunedin flat on our right, bounded by the sandhills in the distance, and at the Kensington Crossing a fine exposure of spheroidally weathered basalt presents itself.

From the Dunedin station the railway follows generally the outline of the harbour, and as we pass, attention is naturally directed to the great excavations in the volcanic rocks, from which enormous quantities of road metal have been extracted. Further on volcanic tuff and trachytic rocks appear, until at Sawyer's Bay sandstone is again met with. This extends right across the harbour to Broad Bay, below Mr Larnach's mansion, which forms a landmark for many miles, and on that side of the harbour the formation yields an excellent building stone. At Port Chalmers there is a large quarry of trachyte breccia, of which the graving-dock at that town is built, as are also partially many of the large public buildings in Dunedin. Over the Mihiwaka tunnel lie volcanic tuff rocks, in which thin seams of coal have been found. In June 1886, while prospecting operations were being carried on, the writer had an opportunity of examining these deposits, and observed a two-foot seam of carbonaceous shale, with thin seams of jetty coal, dipping S. 15 deg. E. at 9 deg. It was stated that in a short distance the thickness increased to 4ft. 6ins. Further down the hill the seam dips at 35 deg. to the south-west, and is much faulted and broken; it was here only 2 or 3 inches thick. Shortly after leaving the last tunnel, we creep along the Purakanui cliffs, looking down from a giddy height upon the green waters of the Pacific Ocean, lazily lapping the base of the rocks below, or surging and boiling with the fury of the storm. From the other side of the elevated portion of the railway, Blueskin Bay is exposed to view, at high tide a lovely bay, encircled by bush-clad hills, and almost enclosed by a