344 Transactions. — Geology. 



Art. XL VI. — On the Drift Beds of Wakapuaka and Port Hills, ivith Remarks 



on the Boulder Bank and its Formation. By W. Wells. 



[Read before the Nelson Philosophical Society, 3rd March, 1884.] 



Abstract. 



I have chosen this locality for my paper from its proximity to the township, 



so that members who take an interest in geological science may have no 



difficulty in visiting the district, which may tend to invite discussion on a 



future occasion, and assist in verifying, or otherwise, the conclusions I may 



have come to on the subject. 



Drift in geological language means portions of the earth's crust removed 

 by forces from one place and deposited in another, some from comparatively 

 short distances and others very wide apart. These forces are of various 

 kinds, the most important of which are, Fire, Water, Ice, and Wind — 

 Fire exhibited in volcanic action, which is powerfully exemplified on the 

 west coast of the North Island, from Mount Egmont to Wanganui. This belt 

 of country is chiefly composed of pounded pumice stone, in some places many 

 feet in depth, which has been erupted from volcanoes in that district and 

 drifted by wind currents all along the belt, now producing the luxuriant 

 grasses which exist there for the feeding of cattle and sheep. Water, the 

 next force I have noted for effecting changes on the earth's surface, is by 

 far the most important, being constant and continuous. The smallest 

 rippling stream to the largest river are daily engaged in transporting 

 matter from a higher to a lower level, as instanced on a large scale — the 

 Canterbury Plains, the soil of which is the degraded high lands brought 

 down by the force of water to nearly sea-level. Ice glaciers you are all 

 aware are forces which carry in their course large quantities of rock and 

 debris and deposit them at a low level in what are called " moraines." 

 The last noted is wind force, which drifts lighter materials, such as fine 

 scoria and pumice dust in volcanic countries, in some cases for hundreds of 

 miles from the mountains from which they have been erupted. 



With these preliminary remarks on drift beds and the forces which 

 occasion them, I now come to boulder drift on a small scale, seen on the 

 Wakapuaka Eoad and Port Hills. 



This drift shows itself on what we may call a raised beach, commencing 

 at the town boundary, and exposed on bare faces for several miles towards 

 Wakapuaka. This beach is raised at a high angle, in some places not less 

 than 45 degrees. In the clay drift on these faces we find stone boulders 

 stuck through it, somewhat like plums in a pudding. These boulders are 

 generally round in form and smooth in surface, showing they have been 

 carried from a distance, getting their round slape and smooth surface from 



