398 Geology of 



proposed by Italian engineers and natural philosophers, the following 

 formulae will conclusively show that all the principal physical features 

 can be explained by them : — 



1. " The more a river advances from its sources, the less will be the 

 declivity of its bed." Or stated differently — " All rivers dispose their 

 beds in the lower course on a less slope than they had in the upper, so 

 that the declivity diminishes in proportion to the distance they have to 

 run from their sources." This law holds good for slowly flowing 

 rivers, depositing ooze only, as well as for rivers and torrents, rolling 

 boulders, gravel, and shingle, because the largest material is gradually 

 left behind. 



2. " The greater the ordinary body of water is in a river, the less will 

 be the slope of its bed." Or, stated in other words — " The slope of the 

 bed of a river will diminish in the same proportion in which the body 

 of water is increased." 



These two natural laws will be quite sufficient to explain all the 

 principal phenomena which our rivers exhibit, the more so as none of 

 them south of Banks' Peninsula have formed a delta properly speaking. 

 The only river possessing such complete features is the Waimakariri, 

 which in its lower course shows great resemblance with the lower part 

 of the Po, in the Plains of Lombardy, which for many centuries has 

 caused anxiety for the safety of the surrounding country, its bed 

 having been raised gradually by embankments to such an altitude 

 that it runs in many localities above the level of the plains on both 

 sides. 



We must conclude that the Canterbury plains are formed by the 

 outlets of enormous glaciers, large torrents bringing down with them 

 the morainic matter, thrown in their course at the terminal face, raising 

 their beds and shifting their channels at the same time so as to form 

 fan-shaped nuviatile accumulations, consisting of shingle, gravel, 

 sand, and glacier mud. In applying the preceding rules, we shall 

 find that as the sources of the post-pliocene torrents were at the 

 terminal face of the glaciers, they lay much further to the east than 

 the present ones, and at the same time, those glaciers being on such a 

 gigantic scale, the torrents issuing from them must naturally have 

 been so much the larger. In consequence we ought not to feel any 

 astonishment at observing, if we take into account both circumstances 

 of the retreat of the glaciers combined with their diminution, that the 

 rivers cut new courses into the older deposits in recent times, the 



