Drs. Orowan and Perutz have shown that glacier ice does not behave as a viscous fluid but is plastic like all crystalline materials. The present author discusses two observed types of ice flow:—(1) the normal, regular streaming flow in slow-moving glaciers; (2) Block-Schollen movement in swiftly flowing ice. Mention is made of the shear plane or laminar flow theory of Philipp. lt appears that Orowan s thesis is also applicable to Block-Schollen flow. The author agrees with Orowan on the fundamental point that when ice is subjected to shear stress a critical value of the shear stress exists beyond which the ice alters its consistency. But the author disagrees with Orowan in that he believes that below this critical value ice behaves as a viscous material, and he supports this view by reference to many phenomena, measurements and calculations.

A recent event of great importance has been the inception of officially sponsored snow research in Canada.

Hitherto large scale snow research has been almost entirely restricted to the Swiss and it is good to know that the Empire with its enormous opportunities will now be playing its part. The connection between the mechanics of soil and the mechanics of snow has been obvious for several years in Switzerland where the resources of the civil engineering laboratories have been made available for snow research. Dr. R. Haefeli, originally a civil engineer and head of the soil research department of the Eidgenossische Technische Hochschule in Zürich, has now become one of the foremost authorities on snow and ice. It is satisfactory to learn that this connection of ideas is being followed up in Canada. In England too a start has been made.

The study of air bubbles in glacier ice can give valuable information on the evolution of the ice. An analysis of the relation between an air bubble and the water associated with it shows that it may be possible to determine the maximum depth from which the ice containing the bubble has emerged. The shapes of the cavities containing water and air bubbles are described. They are found to reflect the anisotropism of ice crystals and reveal that the main crystallographic axis is polar. The question of the mechanism of elimination of air bubbles from glacier ice is raised. The investigations were made on the very old and coarse-grained ice from the foot of the Malaspina Piedmont Glacier in Alaska, which is a temperate glacier.

The photographing of snowflakes has been carried out for many years and has yielded valuable as well as beautiful results. But the unsubstantial nature of snow necessarily makes the process laborious and slow.