TRANSACTIONS OF SECTION J. 481 



As the land rose out of the sea the rivers cut through the 

 blue clay, and, then- beds becoming flatter as the sea retired 

 and the mountains were reduced in height, the former rocky- 

 gorges were filled with the wide deposits of shingle which form 

 the present river-beds. At the same time all the deep bays 

 and hollows between rocky hills were filled up with the accumu- 

 lation, and the present features of the coast-lines were defined, 

 showing now the blue clay and other sea-deposits separated 

 from the sea-shore by a more or less wide strip of gravel, 

 boulders, silt, and sand of comparatively recent origin. It 

 would not be prudent to pursue this theory further, as it may 

 incur the denunciations of the geologists. 



In speculating on what becomes of the gravel brought 

 down by the rivers, the enormous power of the sea in grinding 

 up the hardest material must never be forgotten. The scrubbing 

 by the waves on the beach never ceases day or night, and the 

 hardest stone is reduced to sand in a very short time. I have 

 noticed large rocks of basalt, placed to protect the railway at 

 Timaru, in a few years not only rounded and polished, but 

 reduced to half their original size ; and on man}- beaches it is 

 seen that the size of the shingle diminishes the farther it 

 travels — it has only to travel far enough to become reduced to 

 the finest sand. I assume therefore that there is sufficient 

 evidence to show that the shingle on the west coast constantly 

 travels northwards, and before reaching Cape Farewell it is 

 ground to sand ; what is not dispersed over the sea-bottom or 

 blown ashore arrives at the west entrance to Cook Strait, 

 where it meets a total change of condition in opposing currents, 

 it is driven into the mouth of the strait by the easterly tidal 

 currents and the prevailing westerly winds, and forms that 

 remarkable feature called Farewell Spit, which is about 

 eighteen miles long, enclosing part of Golden Bay. It is 

 always extending, as shown by the great extent of shallow 

 water in front of its end, and it will most likely enclose the 

 entire bay and form a lagoon of it. 



Following up this speculation to the "bitter end," the infer- 

 ence is that the shingle of the east coast of the South Island 

 also travels north, and is finally ground to sand ; v\^hat is not 

 blown ashore is first of all deposited oii the sea-bottom at the 

 east entrance to Cook Strait. From that position it is drifted 

 into the strait by the stronger westerly tidal currents, and, 

 after being shifted backward and forward by opposing tide- 

 rips, it finally emerges at the west end of the strait. Here it 

 mingles with the fine sand and other deposits which the 

 northerly currents have brought up the west coast, travelling 

 in deep water, and the whole is deposited, and forms that 

 great bank of shallow water contained in the wide bay between 

 Capes Farewell and Egmont. 

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