22 THE VICTORIAN NATURALIST. [Vol. XXIV. 



than rivers begin to destroy it. Ideal delta-fans were noticed, 

 and the mode of their formation studied. It was seen how 

 rivers flowing over such formations are forced by their own 

 energetic work to continually find new channels, owing to 

 the rapid deposition of sediments filling up the earlier-made 

 channels. It was clearly seen how a number of delta-fans 

 could coalesce, and plains — such as the Canterbury Plains 

 of New Zealand — be formed. It could easily be seen why 

 it would be useless work to bridge such rivers, and why many 

 of the rivers of the South Island of New Zealand are left 

 unbridged. 



To the north of the cemetery the marvellous effects produced 

 by running water during the last fifteen years in the soft tertiary 

 sands and clays were observed. The amount of water that has 

 produced this earth-sculpturing must have been comparatively 

 small, for its " gathering ground " covers only a few hundred square 

 yards. Yet here we see the whole countryside carved out into 

 canyons with fantastically wrought sides, subterranean channels, 

 natural bridges, residual mountain ranges, mesas, subsided areas, 

 &c., giving the spectator a perfect replica on a small scale of the 

 *' bad lands " of Dakota and North- Western Canada. In one 

 place the water had carried down such a load of sand that it had 

 barred up another stream into which it had flowed and had formed 

 a lake. Thus we were able to notice one way whereby rivers may 

 make a lake, which they would subsequently fill. Attention was 

 drawn to the mode of formation of the surface crust of the land. 

 This crust, which in some places was a couple of feet thick, is 

 due to a cementing, caused mainly by the lime and iron salts being 

 left in the surface of the plain after water in which they are dis- 

 solved has ascended from below and then evaporated. It was 

 owing to the breaking of this surface crust by the ploughing of 

 drams that the running water was able to corrode the softer rock 

 below, with the surprising effects we noticed. The manner in 

 which a river deepens and widens its valley, and in places forms 

 alluvial flats, tends eventually to give it an even, gentle grade 

 throughout its whole course from source to mouth. This was well 

 seen. The material the river uses for eroding its bed and banks 

 was examined, as were also the manner and place of deposition of 

 this material. Small sections cut showed this material laid down 

 in such a way that it gave very good ideas of the meaning of 

 " current-bedding." 



The young folk with me seemed genuinely interested in the 

 afternoon's observations, and tackled the problems suggested to 

 them by what they saw in an eager, open-minded fashion ; and 

 in conclusion I must state that we formed a happy little party, 

 and all spent a pleasant and profitable afternoon together. — 

 R. W. Armitage. 



