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of a yellowish volcanic tuff, intermixed with pumicestone , and it 
is strange enough, that the brittle rock should withstand such a 
powerful swell of the water. The bridge consists of a Totara log 
hewn out in the shape of a flat canoe; it is safe enough even for 
horses. A few yards above the bridge, on the left bank of the 
river, and on a tabular rock, which in time of high-water is flooded 
by the rapid stream, a very striking phenomenon presents itself. 
In the bed of the rock there are numerous round holes, one to 
three and even four feet wide, and equally deep, appearing as if 
wrought by art; in each of those holes there is a stone, sometimes 
two or three, all round like cannon-balls, consisting of hard trachyt 
or dolerit. I stood for a moment wondering what it meant; but 
the interpretation of it is very simple. These pot-holes are evi- 
dently caused by a process of erosion , during the rapid flow of the 
river over the bed of the rock. Any obstacle causes the waters to 
move in a whirl and carry around pebbles or stones, and by this 
process the stones gradually grind their way into the rock. The 
hole being once started, it is bored deeper and deeper, the eddying 
waters keeping the pebbles and stones in a constant rotatory motion. 
Thus the stones grind a circular hole into the rock, and are them- 
selves ground off into balls. The phenomenon is interesting enough 
to induce the traveller to walk a few yards up the river; to step 
upon the rocky bank, which is quite dry at an ordinary stage of 
water; and there to look at the pot holes. Just opposite the Pokai- 
whenua (i. e. boring its way into the earth), empties through a narrow 
gorge into the Waikato. The height of the Waikato above the 
level of the sea near Aniwhaniwha I found to be 166 feet; conse- 
quently from lake Taupo to this place , a distance of about 70 miles, 
the river falls 1080 feet, forming rapids upon rapids; and only a 
few miles farther down it commences to be navigable for canoes. 
Having scaled the pumicestone-terraces on the left bank of the 
river to a height of about 250 feet, we stood at the foot of the 
Maungatautari. Numerous , small tributaries of the Waikato have 
their source in the forests and ravines of the mountain. At a northern 
spur stands the Pah Wliareturere, where we were kindly received 
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