388 Transactions. — Geology. 
subsidence, but also that this subsidence has 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? Why are 
there no broad level gravel deposits like the Canterbury 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 
_ grundmorinen, or moraines profondes of glaciers. 
