Geological Survey of Canterbury. 3 



several extinct craters, mostly submarine, that the ridge or caldron 

 wall to be pierced by the railway tunnel was built up by a great 

 number of basaltic lava streams, beds of tufas and agglomerates of 

 varying thickness, dipping at an average angle of nine degrees to the 

 north, and that the deposits were traversed by vertical dykes of 

 trachyte, filling fissures passing through them, and having been injected 

 from below. As this was the first instance of an ancient crater wall 

 of large dimensions being passed through by a tunnel, from which 

 valuable geological data could be obtained, I followed the work as it 

 proceeded, with a considerable degree of interest, and in the geological 

 description of Banks Peninsula I shall be able to give some details of 

 no mean scientific interest, which these important engineering works 

 disclosed. 



During my stay in Canterbury the Provincial Government did me 

 the honour to offer me the appointment of Provincial Geologist, which 

 I accepted ; and, after going back to Nelson for a few weeks, I 

 returned to Canterbury towards the middle of February to begin my 

 labours. 



EXPLOEATIOJTS OF THE ElVEES Ba^GITATA AND AsHBUBTOtf, 



1861. 



In order to obtain a general insight into the geology of the 

 country I selected the Eiver Eangitata to its ' sources as my base of 

 operations. And after the necessary preparations were made, I started 

 on the 20th February, 1861, for that river, accompanied by my friend 

 the late Dr. A. Sinclair, who went with the intention of assisting me 

 in the botanical researches to be made in the mountain ranges. 

 Until June of the same year I examined this river as well as the 

 Southern Ashburton and their different main branches to their very 

 sources, fixing on the unsurveyed ground all the principal topo- 

 graphical features. This journey brought us into Alpine regions 

 of imposing beauty and grandeur, only surpassed by the still more 

 sublime scenery which further explorations of the central Alps 

 round Mount Cook revealed during the course of the next year. 



Following the valley of the Northern Ashburton, we reached on the 

 26th February the remarkable broad opening in the ranges by which 

 the valleys of the Rangitata, Ashburton, and Eakaia are united, and 

 of which a considerable portion is filled by morainic accumulations r 

 between which a number of small picturesque lakes are situated, 



