The results of the scientific study of snow and avalanches begun at the Weissfluhjoch, Davos, under the direction of the Swiss Commission for the Study of Snow and Avalanches (Schw. Schnee- and Lawinenforschungskommission) were first summarized in the publication Der Schnee and Seine Metamorphose in 1938 by H. Bader, R. Haefeli, E. Bucher, J. Neher, O. Eckel, and Chr. Thams.Footnote *

In 1948, after ten more years of research, Dr. E. Bucher, now Director at the Weissfluhjoch, published a new treatise on snow for his Doctor’s thesis. In this he studies snow as a structural material and finds that this mixture of air and ice is a plastic and compressible substance which, within certain limits, obeys Newton’s law of viscosity. For each type of snow a coefficient of viscosity can be determined and this enables the engineer to make most of the calculations necessary for the construction of avalanche defences.

The viscosities, which vary within wide limits according to the different kinds of snow, clearly explain nearly all the observed phenomena of the snow cover, such as the varying degree of solidity of different kinds of snow deposits, the pressures and tensile stresses of inclined snow strata, the factors governing the release of avalanches and the like.

Thus, for example, since new snow is highly plastic, a deep snowfall becomes a very compact deposit, because it settles under its own weight. On the other hand a thin layer, formed in early winter and lying for a long time unprotected by a new fall, undergoes metamorphosis ; the needles and stars become grains. This granular snow has little plasticity and does not settle when new strata of snow are deposited on it. On the contrary it is brittle and breaks up at the slightest jolt, so that it may at any time cause an avalanche.

The study of the slow creep of inclined snow strata has enabled the author to solve the problem of the pressure of snow against barriers and to draw simple and logical conclusions for the proper construction of avalanche defences. In the case of snow without cohesion the layers can be rendered more stable by reducing the gradient of the surface by means of walls and fences of sufficient height, behind which the snow can accumulate to form a slope of less steepness than the underlying ground. In the case of slab avalanches the downhill tensile stress can be neutralized by barriers built along the contour lines at places where the gradients increase.

In addition to excellent photographs and a large number of clear diagrams there is a very full bibliography containing no less than 236 references. Dr. Bucher’s work marks important progress in the study of snow. It indicates numerous practical applications and opens up a vast field for further research.