THomson.—Glacial Action in Otago. 321 
esteemed a circumstance of high geological importance and interest, and 
contribute to throw some further light on the physical construction of our 
globe. I named it ‘Mount Erebus,’ and an extinct volcano to the eastward) 
little inferior in height, ting by measurement 10,900 feet high, was called 
* Mount Terror.’” 
Again: “ At 4 p.m. (January 28th, 1841), Mount Erebus was observed to 
emit smoke and flame in unusual quantities, producing a most grand spectacle.” 
Again: “ We made good progress to E.S.E., close along the lofty, perpen- 
dicular cliffs of the icy barrier. It is impossible to conceive a more solid- 
looking mass of ice ; not the smallest appearance of any rent or fissure could 
be discovered throughout its whole extent, and the intensely bright sky beyond 
it plainly indicated the great distance to which it extended to the southward." 
Again: * This extraordinary barrier of ice, of probably more than a 
thousand feet in thickness, crushes the undulations of the waves, and dis- 
regards their violence, It is a mighty and wonderful object, far beyond 
anything we could have thought or conceived." 
Such is the description by an experienced arctic and antarctic voyager of 
a land such as New Zealand had once been in the glacial epoch, and I beg to 
refer you to page 232, vol. l, of his work for an admirable drawing of the 
south polar barrier of ice which he discovered, and which rises 160 feet above 
the sea level, being also 1000 feet thiek and 450 miles in length. With these 
facts before it, then, the mind may be presumed to be in preparation to perceive 
how the great erosions of surface had taken place here. The effects we see, 
and the power, indeed, is undeniable ; for within six days' steaming from this 
we have the very extremes of the terrene glaciers, which have for ages been 
subject to the melting influence of the sea, yet maintaining a thickness of 
1,000 feet, then in the valleys and at the mountain bases we have a right to . 
conclude that in such places the glaciers may exceed 2,000 to 3,000 feet in 
thickness, Such being the case, then, the eroding force is only a matter of 
mere rule-of-three calculation, as below :— 
Ice weighs 59Ibs. per cubic foot. Ice, then, 1,000 feet in шай will 
have a erushing power of 4091bs. per square inch ; of 2,000 feet, 818Ibs. ; and 
of 3,000 feet, 1,2278. Now, chalk, according to Rankine (which has about 
the consistency of Caversham limestone), is crushed under a weight of 33018, 
per square inch. Thus, in the glacial epoch, would the Kaikorai Valley be 
scooped out by nature in as easy a manner as the potter's tool shapes the clay 
vessel Limestone, such as most of that to be found on the Oamaru Plains, 
crushes under 2,200ibs. per square inch ; this, then, with the alternate clays 
and soft shales, under half or third of the pressure, would yield to the glaciers 
of the thickness above given when in motion ; and, when not in motion, yet the 
more readily by the power of water, under hydraulic pressure, finding its way 
Yi 
