388 Transactions. — Geology. 



subsidence, but also that this subsidence lias been greater on the west than on 

 the east coast ; consequently, according to his theory, the velocity of the 

 rivers must have been considerably reduced, and he has not informed us how 

 it is that they have been enabled with their reduced velocities to cut through 

 and remove the alluvium which they could carry no further, but deposited 

 when their velocity was greater. 



All these things, as well as the occurrence of vegetable deposits below the 

 gravel, are readily explained by supposing the plains to be a marine formation 

 since elevated, but are, I think, quite inexplicable on the river formation 

 theory alone. I might also fairly ask, if rivers form such large level plains in 

 New Zealand why do they not form the same in other countries 1 Why are 

 there no broad level gravel deposits like the Canterbui-y plains round the foot 

 of the Himalaya, Alps,*, etc. ? My answer would be because none of these 

 places have been lately submerged below the sea. 



That the greater part of the shingle of the Canterbury plains has been 

 brought down by the rivers from the mountains I do not dispute, and I also 

 acknowledge that, as the plains were elevated, the rivers must have often 

 changed their courses and wandered over a large part of the plains near the 

 then shore line, all that I contend for is that the materials brought down by 

 the rivers have been rearranged by the sea, and the shape of the stones would 

 therefore depend upon the length of time that they had been subjected to 

 wave action, and on the amount of sand in which they are imbedded. The 

 silt deposit upon which a large part of the town of Lyttelton is built is also 

 evidently a recent marine deposit, but I do not know to what height it 

 extends above the sea. 



Mr. W. T. L. Travers has pointed out to me that the land side of the hills 

 forming Banks Peninsula shows no trace of marine erosion, and this is the most 

 formidable objection to the elevation theory that I have as yet met with. It 

 would be very easy to say that as Banks Peninsula is volcanic it may have 

 been thrown up or elevated more rapidly than the plains, and at a later date, 

 but there is no proof of this, and until that can be given I could not accept it 

 as an escape from the difficulty, but we must remember that the land side 

 would not have been exposed to a heavy surf, and that the rapid decomposi- 

 tion of the volcanic rocks might soon obliterate all traces of a sea cliff. Mr. 

 C. Forbes states (" Q. J. Geo. Soc," 1855, p. 526) that "there is abundant 

 evidence to prove that at a very recent period the Peninsula was an island." 

 The absence of fossils in the Canterbury plains is easily explained, indeed we 

 could hardly expect any to occur, for those shells that were not completely 

 pounded to pieces on the shingle beach would be rapidly dissolved out, on 



* The gravel deposits of Switzerland are of quite a different character, and are the 

 grundmwdnen, or moraines profondes of glaciers. 



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