Canterbury and Westland. 175 



the subject, in that district, and I may here be allowed to quote from 

 his valuable report,* the principal passages having reference to the 

 subject : — " The next feature to be noticed is the jointed structure of 

 the rocks. Although they cross each other in all directions, apparently 

 without order, there are two systems of joints which are to be met 

 with throughout the whole valley of the "Waimakariri, and which have 

 an important influence on the configuration of the Passes. These 

 are — (1st) A system of vertical cross joints at right angles to the 

 stratification, and running in unbroken lines for great distances with 

 such regularity that they might easily be mistaken for planes of 

 stratification, were it not for the frequent occurrence of beds of trap 

 rock, the outcrop of which marks unmistakably the true bedding. 

 (2) A system of joints more or less inclined to the horizon, not 

 running in parallel planes, but arranged in a series of curves radiating 

 from a common centre. The effect of this system of jointing is to 

 produce a rectangular arrangement in the plans and sections of the 

 ravines ; the rivers and water-courses running either on the strike of 

 the beds or in the direction of the cross joints, or in a zigzag course, 

 following alternately these two directions, as in the annexed sketch 

 (fig. 2), which shows the character of the valleys connecting the 

 "Waimakariri and Teramakau, which have generally a northerly 

 direction, thus making an angle of about 22 deg. with the strike of the 

 strata. In consequence of the vertical position of the strata, and the 

 inclined position of what maybe called, for convenience of description, 

 the horizontal joints, the sides of the ravines present either sheer 

 precipices or dangerous slips, according to the extent to which the 

 rocks have been loosened by exposure to the rain and frost ; and the 

 result is, that to form a road inside cutting through any of these 

 ravines is simply impossible." 



Mr. Dobson, in the same report, points out a very interesting and 

 suggestive fact which had not before been noticed, namely — that all 

 the principal valleys, from the Hurunui in the north to the Makaroa 

 in the south, radiate as it were from a common centre, situated about 

 50 miles to the north of Mount Darwin, or about 40 miles west of 

 Hokitika. This remarkable phenomenon is more than a coincidence, 

 and it would not, therefore, be too rash to conclude that, during or 



* Eeport to the Secretary for Public Works upon the Practicability of Constructing a Bridle Eoad 

 through the Gorge of the Otira, and upon the character of the Passes through the dividing range of 

 the Canterbury Province. By E. Dobson, C.E., Engineer of the Lyttelton and Christchureh 

 Eailway. With forty illustrations and an appendix. 



