174 Physical Geography of 



steep folds, which have been so much denuded, that the synclinals or 

 lower portions of the folds now form the summits of the mountain 

 ranges, whilst the valleys are generally formed along the anticlinals 

 or saddles. In some instances, the valleys run, at least for some 

 distance, with the strike of the beds, but in others, diagonally or 

 across it, and we have to search, therefore, for some other cause by 

 which this peculiarity has been brought about. 



Whoever examines our mountain ranges must be struck by the 

 enormous waste which is going on without interruption amongst them. 

 There are mountains 7000 to 8000 feet high, which are covered with 

 angular fragments of rock from summit to foot, and from which only 

 here and there strong buttresses of rock prominently stand out, more 

 or less split up on their surface. In examining these angular frag- 

 ments (usually called shingle in Xew Zealand, whence the expression 

 " shingle slips " for these huge taluses of debris covering the mountain 

 sides), we find that they have a polyhedrical shape, their planes being 

 sharply defined, and cutting, as seen in the conglomerates, clean 

 through even the hardest pebbles of which the latter are composed. 

 If, on the other hand, we examine the rocks in situ, either on the 

 mountain sides or in the river gorges, which in many cases have been 

 cut through only in comparatively recent times, we observe that all 

 these rocks are jointed in a very striking manner. These joints run 

 in such various directions, and appear so conspicuously, that in many 

 instances they conceal the original stratification altogether. The 

 latter occurrence is chiefly observed where large series of very thickly 

 bedded sandstones form the ranges. It is well known, and has been 

 practically proved, that joints are the result of great pressure 

 exercised upon the rocks, the joint having been formed at right angles 

 to the direction of the pressure. 



In the geological portion of this report, I shall return to this 

 interesting subject, but wished to refer to it here so far as the physical 

 features of the country have been influenced by this peculiarity in the 

 structure of the rocks. There are mostly five distinct sets of joints 

 observable, of which some are more or less conspicuous. In many 

 localities, one of theprincipal joints generally appears at right angles 

 to the stratification, the others passing in various but well defined 

 directions. It is evident that the internal forces by which these 

 joints have been formed must have acted from various directions, 

 sometimes nearly opposite to each other. Mr. E. Dobson, C.E., 

 when laying out the Otira road, made some important observations on 



