292 Transactions. — Geology. 



I have come to the conclusion that at a time when the present entrance to 

 the harbour was closed, and when Port Nicholson was a fresh-water lake, the 

 boulders of the isthmus mark a river bar — not a bar at the mouth of the river, 

 but a bar at the foot of a pool or lake and above a rapid — probably accumvdated 

 against a ridge of hai'der rocks. That this bar must have been re-aiTanged 

 and altered by the sea at the time when the land was depressed some fifteen 

 feet below its present level is sufiiciently obvious, and accounts for its present 

 appearance as having been latterly a niai-ine boulder bank, under somewhat 

 similar conditions to that at Napier, although different as lying between two 

 bays. 



When we consider the matter ftilly, it seems a necessity that Port Nicholson 

 must have been formerly a fresh-water lake. The borings taken from the 

 wharf showed the remains of land vegetation at a considerable depth. There 

 are numerous other reasons to suppose that, with the exception of the before- 

 mentioned rise of fifteen feet, there has been a long era of depression, and that 

 consequently the land must formerly have stood at a much higher elevation. 

 One feature is, I think, conclusive as to a certain amount of elevation, viz., 

 the present entrance of the harbour. From the remains of Barrett Reef and 

 other rocks it is evident that this entrance or passage has been excavated 

 chiefly by denudation. Now, it is impossible to suppose this to have been 

 done by the ebb and flow of the tide. The requisite effect is to be easily 

 accounted for by supposing Port Nicholson to have been a fresh-water lake with 

 an outlet in Evans Bay. From the erosion of the coast line the locality of the 

 entrance of the harbour became weakened, the waters took that direction and 

 scoured out the channel, leaving the old Evans Bay passage high and dry. 

 Supposing the present entrance of the harbour closed, Port Nicholson would 

 even now become a fresh- water lake, with an outlet in Evans Bay; and taking 

 the mean elevation of the isthmus at fourteen feet above high-water mark, and 

 supposing a depth of stream of only five feet, the waters of the harbour or 

 lake would be raised so as to submerge a large part of the Hutt Valley, 



On the other hand, taking the mean depth of the harbour and entrance at 

 ten fathoms, if we suppose a rise of the land of sixty to seventy feet, we should 

 have a fresh-water lake, although of diminished area, even with the present 

 entrance open. I think it will be found that the barrier was originally 

 sufficiently high to form a lake extending up the valleys of the Lower and 

 Upper Hutt, and that the deposits which have filled these valleys are from the 

 talus of the river drifts falling into a lake. There appear, in the Hutt Valley, to 

 be deposits of heavy boulders succeeded by gravel and clays, and finally by 

 fine alluvium, the latter lately covered by a magnificent forest, now almost 

 entirely destroyed by man. 



No strata of marine origin appear to be found in the Hutt Valley. Had 



