Page:Mannering - With axe and rope in the New Zealand Alps.djvu/159

Rh In exposed sections and upon the surface of the ice can be observed a 'veined' or 'banded' structure—veins of a denser blue colour alternating with those of a lighter shade containing air bubbles.

The cause of this peculiar structure has been the subject of much theorising amongst investigators, but hitherto I believe the greatest authorities consider that the explanation of the phenomenon is yet wanting.

The motion of glaciers is yet another bone of contention, but it is generally admitted that the cause of it is to be found mainly in gravitation, and is also partially accounted for by the strange property of 'viscosity' in what appears to the casual observer to be nothing more or less than a rigid solid.

Recently observations for ascertaining the rate of progress of the Tasman, Murchison, Hooker, and Mueller Glaciers have been made by the New Zealand Government Survey Department. Some of the results were embodied in a paper by Mr. J.H. Baker, the Chief Surveyor of the Provincial District of Canterbury, and will appear in the 'Transactions of the Australasian Association for the Advancement of Science' for 1891. At the late meeting of that body a committee was appointed to further these investigations, and a sum of 25l. voted for the aid of the same.

Before long, therefore, there will be put before the scientific public reliable measurements of the motion of several of the largest and least-known glaciers in temperate regions.