WoKLEY. — On the Nelson Boulder Bank. 225 



The remarkable position of the ba-nk, standing as it does 

 some distance away from the shore-Hne of the inner harbour, 

 is another difficulty. Why were the boulders not driven right 

 in shore by those mighty seas, and piled up along the beach ? 

 It is all very well to speak alDout the opposing forces of the 

 tides in the harbour; but where was that force when the bank 

 was only a mile or two long? It did not then exist. 



The last difficulty that I shall mention is the finding of 

 stones on the Boulder Bank that are not to be found at 

 Mackay's Bluff. On that part of the Boulder Bank lying 

 south of the lighthouse there are numerous boulders of red 

 syenite. This red syenite is not to be found at Mackay's 

 Bluff. It, however, forms a part of the Arrow Eock, and the 

 cause of its redness is there also apparent. When speaking 

 of the composition of the Arrow Kock reference was made to 

 an intrusive sheet of lava that had invaded the syenite. This* 

 lava contains much iron, and the syenite in contact with it 

 has been stained red by the oxide of iron produced by de- 

 composition of the lava. There are also on this part of the 

 bank boulders of a very fine-grained rock which does not 

 appear at Mackay's Blufl', but is found on the Arrow Eock. 

 Having carefully examined the beach at Mackay's Bluff, the 

 southern end of the Boulder Bank, and the Arrow Eock, I am 

 fully convinced that the points of similarity between the rocks 

 on the Boulder Bank and those of the Arrow Eock are far 

 more striking than the same rocks compared with those of 

 Mackay's Bluff. 



Enough has now been said to show that the origin of the 

 Boulder Bank is a question not easily settled simply by ob- 

 servation and reasoning. The sinking of a shaft on the 

 bank, however, would probably set the matter at rest. Before 

 attempting to cut the bank this preliminary precaution 

 should certainly be taken. Although a strong supporter of 

 the underlying-reef theory, it would be gratifying to me to 

 find that the reef did not exist, because the faciUties for 

 improving our harbour would be then greater than I now 

 consider them. If, on the other hand, a solid wall of syenite, 

 or of firmly cemented syenite boulders, does underlie the 

 bank, it would be well to know the truth before spending 

 large sums of money on a work that might never be com- 

 pleted. 



What has been said about the probable reef-formation of 

 the Boulder Bank applies with equal force to the submerged 

 banks within the harbour. As they too would have to be 

 cut in carrying out the proposed harbour improvements, it 

 would be necessary to test them also by boring to the required 

 depth. 



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