Thomson. — Glacial Action in Otago. 325 



and which, also, have numerous rivulets running into and joining them, we 

 will have the exam2iles required. Then observe the banks of the lake or river 

 at full flood, and you will see no indications of terraces, unless under water. 

 Above the flood-line, no doubt, will be seen the terraces of former ages, but 

 within the limits of rise and fall of the lake or river itself is only to be seen 

 the action, in miniature, which is of use in illustration. Then it is by receding 

 waters, or waters that have receded, that the terraces became apparent — of a 

 river or lake in a few months ; of the great ocean in many centuries. Yet the 

 action and results are precisely similar; for, looking at the conformation of the 

 surface of the shores of a lake or river where the feeder, or rivulet, entei's, you 

 will see the slopes divided into terraces : highest near the flood marks, lowest 

 near the low water ; most inclined near the flood mark, least inclined near the 

 low water ; the largest particles or pebbles near the flood mark, mere sand or 

 mud near the low water ; thus conforming, in every respect, to the gigantic 

 formations which we are now considering. And let two streams enter a lake 

 or river closely adjoining — the spurs between will be the same — sloping with 

 the opposite terraces, and the talus will reach out in the manner that the 

 receding waters had tended. . If this be the law in small areas, so it is in great. 

 It is, therefore (after glacial action had filled up the valleys with debris), to 

 the receding waters of the ocean, assisted by influx and reflux of tide, with the 

 feeder from the mountains at the head, that we may, without fear of 

 contradiction, ascribe the hollowing out of the gullies in the terraces, and the 

 transport of the smaller gravel and sands towards the ocean shores. Thus, 

 while the glaciers brought down the shingle and deposited it all over the valleys, 

 the succeding action of scoring out the terraces themselves into gullies was 

 efiecfced by the land rising, or, in other words, the ocean receding. 



And while we see the terrace formations most prominent in the interior, 

 most inferior near the coast, this is also due to the interior ones having been 

 protected from the ocean surf by the enclosing mountains, while those on the 

 seaboard have been subject to the full force of this degrading power. The 

 whole formation of terraces, as we now see them in Otago, therefore, we may 

 reiterate, have been the result of the mechanical action of nature operating, 

 first in the long period of the glacial age, then afterwards by the rise of land, 

 ■ in which the tides of a receding ocean and the fresh waters of the mountains 

 together acted as moulders of the present forms in their bold fi'onts, long 

 reaches, abrupt rises, deep indentations, and mathematically-curving slopes. 



With the well-known fact before us, that gold is found disseminated in 

 quartz veins, and reefs intersecting the schist rocks, of which the mountains of 

 the interior ai'e principally composed — a fact so intimately connected with one 

 of the most im2:)ortant industrial pursuits — some allusion to it is called for. The 

 allusion must necessarily be a mere passing one, as no justice can be done it 



