Teavers. — On the great Floods of February, 1868. 81 



A number of small valleys, lying generally at right angles to the course of 

 the main river, occur amongst the spurs of the mountains on each side of the 

 gorge, each of which has its own stream, whose size is proportionate to the 

 extent of the valley in which it flows. Every one of these lateral valleys is 

 filled with gravels to about the same height as the level of the higher part 

 of the Hurunui Plain, and its front towards the main river, between the 

 extremities of the spurs which bound it, is a terrace face equal in height 

 to the difference between that of the upper surface of the Hurunui Plain 

 and the surface of the gravels of the terrace at its foot. From this foot to 

 the edge of the bank of the main river the width varies from fifty to three 

 or four hundred yards, and it is along this terrace that the road runs. 



Now each of the streams which occupy these lateral valleys has cut a chan- 

 nel, more or less deep, through the gravels with which its own valley is filled, 

 and, in some instances, through the rock which underlies them, and de- 

 bouches on to the terrace of the main river, over which it flows in a manner 

 having special relation to its magnitude and the force of its current. In 

 every instance, however, these lateral streams have formed, at their debou- 

 chures on to the main terrace, what are geologically termed half-cones, 

 more or less extensive, composed of the gravel and other detritus which 

 they have removed in their courses through their own respective valleys. 

 In some cases, where the streams are small, they become lost after de- 

 bouching from their own valleys in the gravels of these half-cones, their 

 waters then finding their way by subterranean courses to the main river. 



In flood times the waters of these smaller streams spread over the surfaces 

 of their several half-cones, and after flowing beyond them for short distances 

 lose themselves in the gravels of the main terrace. In other cases, where 

 the streams are larger, each of them has cut a channel through the 

 upper surface, but not to the fuU depth of its own half-cone, and after dis- 

 charging its waters beyond the edge of the half-cone, also loses itself, except 

 in flood time, in the gravels of the main terrace, whilst in flood time it finds its 

 way by a number of shallow surface -channels to points beyond its ordinary 

 place of disappearance, and then loses itself in the same manner. 



But there are several of these lateral streams which, after having formed 

 their half-cones, in times long past, have not only cut through the gravels of 

 their own valleys and through the rock below them to a level below that of 

 the surface of the main terrace, but also through their half-cones and the 

 gravels of the main terrace and the rock below them, running into the 

 main river in narrow ravines, varying from ten to thirty feet in depth. 



In flood times streams of this class are raging torrents, bearing into the 

 main river immense quantities of silt and gravel which are carried forward 

 by the larger stream. As may be supposed, however, the beds of all these 



