448 Transactions. — Geology. 



Art. LXXI. — Bid the great Cook Strait River flow to the North-West or 



to the South-East? By J. C. Crawford, F.G.S. 



[Read hefore the Wellington Philosophical Society, 2oth July, 1874.] 



Last year I endeavoured to sliow, and I think with some success, that 

 Port Nicholson had formerly been a fresh-water lake.* The theory was 

 founded more on what necessarily must have been the case, supposing the land 

 formerly to have stood at a higher level, than on actual observation of fresh- 

 water deposits. Possibly these may lie hidden beneath the waters of the 

 harbour, but remains of terrestrial vegetation are found in wells within the 

 precincts of Wellington city much below the present sea level, and have 

 probably been originally deposited in the waters of a lake, and, as observations 

 are extended, I have little doubt that additional evidence will be forthcoming 

 in future. 



I now propose to continue the reasoning on which this theory was founded, 

 to show that a large river must formerly have run through what is now Cook 

 Strait, and consider in which direction it is most probable this river flowed. 



If we consider the somewhat analogous position of the Straits of Dover, we 

 find similar geological formations on the opposite sides of that channel, thus 

 showing that at one time the two sides were continuous. It has been the 

 habit to refer the separation of England from the Continent to some great 

 convulsion of nature, but these violent catastrophes are rather out of fashion 

 at present, and the modern view is that the present line of strait was first 

 denuded and weakened by a large river which ran through the course of the 

 present strait, and of which, probably, the Thames and the Rhine were 

 tributaries, or possibly this river may have been a tributary to the Rhine. 



Now, on the opposite shores of Cook Strait we find the geological strata in 

 the position to infer that formerly there was continuity, and that the islands 

 were joined above water. Probably there may have been greater elevation 

 or depression on one side than on the other, and it is reasonable to suppose 

 that when we get into the volcanic zone of Mount Egmont we find an area of 

 former depression. Nevertheless, we may suppose it to be a certainty that 

 the islands were formerly joined together above the sea level. 



Are we then forced to seek for a great catastrophe to cause the separation 

 of the islands, or would it not be much more reasonable to follow the analogy 

 of the Straits of Dover, and suppose that a large river first denuded and 

 weakened the channel, by forming a valley, which permitted the sea after- 

 wards to complete the work thus begun 'i 



I think wo have sufficient evidence of the powerful work of fresh water 



• Trans. N.Z. Inst., VL, Art. XLVIII. 



