Wells. — On the Drift Beds of Wakapuaka. 345 



I do not think I have anything further to say about the boulder drift on 

 the line of the Wakapuaka Eoad. It would be a very pleasant excursion 

 for any of the members of this Society to take a hammer in hand, traverse 

 the district, aud find the parent rocks from which these boulders have come, 

 and endeavour to trace the course the force of water took in bringing them 

 to the position in which we now find them. 



I may, however, mention here, that as you get higher up on the line of 

 this raised beach, you meet with beds of shells from a few inches to a foot 

 under the surface, at a considerable elevation above sea-level. When these 

 beds were first exposed on the slopes, the impression of the settlers who ex- 

 posed them with the spade or plough was, that the Maoris must have brought 

 them ; but when we find them assuming the same striaa and curved shapes 

 which the tidal current gives them at the present time in our lagoon, or 

 what we call our mud flat, there is no difficulty in coming to the conclusion 

 that they were deposited at sea-level, and subsequently raised by forces from 

 underneath. 



I shall now offer a few remarks on a natural object conspicuous among 

 our surroundings here, viz., the "Boulder Bank." How was it formed, and 

 what were the forces employed in building it ? The first consideration is, 

 where did the material come from of which it is built ? If we travel to the 

 extreme north end of the bank, by Mr. Mackay's property, we will find a bold 

 rocky bluff, nearly vertical, with the sea lashing on its base at flood tide. 

 This rock is local, and does not extend far beyond this point, and is of the 

 class of mineral called syenite, composed chiefly of quartz, hornblende, and 

 felspar, very hard and crystalline in its character. Now if we leave this 

 bluff and walk down towards Nelson on the seaside and examine the boulders 

 which form the bank, we will find them mostly all of the same character as 

 the perpendicular bluff before mentioned. This bluff has been acted upon 

 by the sun's rays on its face on the one hand, and by the sea and spray 

 and rain on the other, whereby its cohesion is loosened, when it gradually 

 falls down into the sea in smaller or larger pieces. These fragments of 

 rock get disturbed by the swell of the sea and by a powerful current which 

 sets down from that point, are then gradually rounded at their sharp edges by 

 rubbing against one another, when they are easily carried forward by the 

 swell and current, and rolled up on the bank where we now find them. It 

 is observable also that the further they get on their journey the less they 

 get in bulk from the grinding process they have to undergo in transit. 



Another feature in this bank is the straight line — north and south — on 

 which it is built. How has this straight line been preserved throughout '? 

 We find there are two forces in operation, an outer and inner current, the 

 swell of the sea and a strong tidal current on one side, which heaves up the 



