Canterbury and Westland. 335 



top of the Bridlepath, it has narrowed to 23 feet 9 inches, after which 

 it gradually gains in proportion, so that in Thompson's quarry it has 

 enlarged to 26 feet, a breadth which it still has in the tunnel. A mile 

 beyond the quarry the spur along which its course can be followed, 

 runs out in the Heathcote valley, where it disappears below the 

 Loess. 



Two remarkable dykes, reaching the summit of Dyke Hill, about 

 2000 feet high, west-south-west of Castlehill, are very conspicuous. 

 They both project boldly from the mountain, *with a space of 35 feet 

 between them. The eastern one is 18 feet, and the western 12 feet 

 broad. Two similar dykes exist on the opposite side, and run up the 

 caldera wall behind Haupaki. To mention a few others, there are 

 some important dykes south of Dyer's Pass, which, after crossing 

 Manson's Peninsula, are again met with at Ohinitahi (Governor's 

 Bay), and of which several, after ascending to the very summit of the 

 caldera, reach to the foot of the Peninsula near Cashmere, being 

 extensively quarried in different localities along their course. These 

 dykes, like many others which cross the caldera wall towards the 

 Canterbury plains, mostly all radiate from a point lying in the centre of 

 the Bay, formed by Manson's Peninsula on the one side, and Potts' 

 Peninsula on the other, both of which consist of quartziferous por- 

 phyries, and between which this newer focus has been formed after the 

 greatest portion of the caldera wall had already been built up. There 

 is also the large dyke which crosses the Lyttelton-Sumner road at right 

 angles, on the very summit of Evans' Pass, and which is repeatedly 

 passed by the road winding in and out the different ba} r .s before reaching 

 that Pass. It can be followed to Taylor's Mistake. Everywhere 

 along the sea cliffs at and near the entrance of Lyttelton Harbour, 

 numerous dykes, mostly all in a vertical position, can be seen pointing 

 towards the centre of that harbour. A few, however, stand in a 

 slanting position, and others have a tortuous course. As one of 

 the remarkable changes which some of the dykes have undergone 

 since their formation, I may also mention one which is well exposed 

 in the seacliffis at Ohinitahi, Governor's Bay ; here, a dyke of domite, 

 about nine feet broad, crosses in a nearly vertical position the so-called 

 trachyte sandstone deposited on the slopes of the quartziferous por- 

 phyry. After its solidification, a new fissure, about three feet broad, 

 has been formed parallel to its direction, and running along its centre, 

 which has been injected from below by domitic matter, but slightly 

 different from the former ; however, instead of continuing to the top 



