﻿336 Transactions — Geology. 



On the east side the water deepened quickly, but on the west side it w^as 

 shallow for a considerable distance. It is situated jnst opposite to tlie main 

 entrance of the Waikari Lake. 



The second new island is situated a little above Ai-mitage's fai'm ; it is 

 smaller now than the first, but has been mvich i-educed in size by a large coal 

 barge having been stranded on the upper part, and the disturbance caused by 

 getting her off has washed a large part of it away. 



It is evident that if these banks are prevented from moving by the roots of 

 the plants growing on them, every flood must increase their height until 

 ultimately they are rarely under water ; so that all that is wanted to form an 

 island is that some unusually high flood should so raise a sand-bank that it is 

 not covered for several months during the season that seeds can germinate, and 

 so allow the plants to grow sufiiciently large for their roots to hold the sand 

 together the next time that it is submerged. Floods in spring might therefore 

 often cause islands, while floods in autumn might fail to do so. 



These remarks on the formation of islands by rivei's must not be taken as 

 applying to rocky masses in a river bed, nor the upper portions of any river, 

 but only to the lower portions, where a large river flows tranqiiilly through an 

 alluvial plain. 



Art. LXII. — On the Traces of Ancient Glaciers in Nelsoti Province. 

 By A. D. DoBSON, C.E. 



[Read before the Nelson Association for the Promotion of Science and Industry, 



3rd May, 1871.] 



The labours and investigations of scientific explorers, especially those so suc- 

 cessfully conducted by Dr. Haast, prove, beyond doubt, that at a very recent 

 period all the higher motmtains of New Zealand were covered with joerpetual 

 snow. Large glaciers filled every valley, and most of the large rivers were 

 glacial torrents. Since that period the climate has become more genial — the 

 glaciers have receded into the mountain gorges, or altogether disappeared, and 

 only the highest mountains are now covered with perpetual snow ; but these 

 earlier glaciers have left traces behind them, shov\^ing the magnitude they had 

 attained, and masses of moraine matter lie scattered over the face of the country 

 in every direction. 



The largest glaciers that existed during what may perhaps be correctly 

 termed the glacial period of New Zealand, lay on the western slopes of the 

 Southern Alps ; enormous masses of loose rock lie stretched in rivers and 

 ridges between Hokitika and Jackson Bay, proving that these glaciers extended 



