260 {OURNAL OF SCIENCE, 
size of glaciers; and Prof. J. D. Forbes cites in proof the fact 
that, while the snow-fall in both places is about the same, “the 
largest glacier in Norway (Lodal) may be rudely estimated to 
have only one-seventh of the surface of the Aletch glacier of 
Switzerland, tributaries in both cases being excluded ; but the 
snow field connected with it may cover 400 English square 
miles at least, which probably exceeds in extent anything in the 
Alps. The perpetual snows of the Fondalen are much larger, 
and those of Sulitelma not inferior.’* The size of glaciers there- 
fore is not proportional to the size of their snow-fields, as 
supposed by the advocates of the plateau hypothesis. Neither 
is the denuding power of the snow so great as supposed. Of 
course the snow-fields themselves preserve the rocks that lie 
below them ; it is only when the snow gets pressed into ice and 
begins to descend the valleys that any erosion can take place; 
but even this erosion has, I think, been greatly over-estimated by 
the advocates of the plateau hypothesis. On this point I gladly 
avail myself of the opinion of Sir A. Ramsay, whom no one will 
accuse of underrating the amount of glacier erosion. In a dis- 
cussion at a meeting of the Geological Society of London, in 
1875, he said that “he thought that the effects of glacial action 
had been immensely exaggerated, and believed that all the great 
features of the country existed before the glacial period ;’+ and 
in the following year, in his paper on the history of the River 
Dee, he says that “ by far the greater part of the valley excavating 
work was performed between permian and pre-glacial times, and 
that the work of the glaciers of the latter period somewhat 
deepened, widened, smoothed, and striated the outlines of the 
mountains and valleys, and excavated many rock-bound lake- 
basins, but on a grand scale did not effect any great changes on 
the pre-existing larger contours of the country.” 
In our own case we must remember that, even if glacier 
erosion is as great as claimed by the advocates of the plateau 
hypothesis, there have been in New Zealand, in the lower 
cretacous and eocene periods, two earlier and probably quite as 
extensive glacier epochs, which must have reduced to ridges the 
supposed plateau, if it ever existed. We must also remember 
that the New Zealand Alps have been undergoing sub-aerial 
denudation without interruption from the jurassic period to the 
present day ; and we have conclusive proofs that most of the 
valleys had been hollowed out nearly as deeply as now in the 
eocene period, because we find all the large river basins partly 
filled with oligocene, or in some cases even with upper cretaceous 
rocks. Iwill limit myself to one example in illustration. In the 
middle Rakaia, on the right bank of the river, opposite the south 
end of Lake Coleridge, there is an outlier of oligocene limestone, 
called Red Cliff. It is lying in its original plane of deposition, 
* Norway and its Glaciers, p. 232. 
tT Quar. Jour. Geol. Soc. XXXII, p. 204. 
+ Quar. Jour. Geol. Soc, XXXII., p. 227. See also Dr, Knight in Trans, N, 
Z. {nst. VII., p. 479. 
