Page:Transactions NZ Institute Volume 10.djvu/41

Rh The "Glacial Epoch" in New Zealand is assumed by Dr. Haast, F.R.S., to have been synchronous with the alleged period of the general reign of frost in northern regions, and we are accustomed to hear of the "Pleistocene Glaciers" as those which have done the most work in the land of the moa. Bui there seem to be very good reasons for placing the age of their greatest extension back in pliocene times, about the time man was learning experience in Lemuria.

When the Cordillera stood at an equally higher altitude as that claimed by Professor Ramsay for the Swiss Alps, we may be well satisfied with the ability of the rain-bearing winds coming round in their sweep back from equatorial regions over the warm Australian Sea to breed glaciers of magnitude sufficient to do all the work claimed for them—to shape the sides of the valleys and glens, scoop out the basins of the southern lakes, grind out the fiords of the west coast, and break up and collect the materials for the formation of the sub-alpine plains, to be spread out there by the torrential rivers in after times, which, as the land has gradually risen again after partial submergence since, have left the remarkable terraces, whose symmetrical lines produce such a striking feature in the landscape—of magnitude sufficient to carry off masses of rock 20,000 tons in weight, if required, and deposit them as blocs perchés below, with as much ease as those masses of Mont Blanc granite were borne along and left on the sides of the Rhone valley. Which operation probably they did perform, but the memorials being of less durable material, have disappeared under the gradual wear and tear of ages, or lie buried under the accumulations of gravel and sand on the plains, or beneath the sea.

In both of these mountain systems, as in the Himalaya, changes in the dimensions of their ice-streams, and debacles caused by the bursting of glacier dams, from time to time occur, on an insignificant scale it is true, when compared with what we may well believe went on in the days of their greatest grandeur, from local causes apparently, but which causes owe their origin to events going on in far distant regions. It is convenient sometimes to compare small things with great, and the operations proceeding quietly now, enable a judgment to be formed as to how the same causes, working with more activity, might readily be able to repeat the phenomena that engage so much attention.

The glaciers in the Swiss Alps, which had been retreating for thirty years, are advancing again at present, those descending from the heights of Monte Rosa are tearing up the green fields and overwhelming the gardens and homes of the peasantry, and, as the alternate advance and retreat of those of Mount Cook and adjacent mountains, present an evidence of the effect of ocean currents upon regions apparently far removed from their influence.