In a letter to the reviewer, Mr. J. M. Herbert, Assistant Chief of the Division of Recreation and Lands of the U.S. Forest Service, writes that in addition to being interested in glaciology from a water yield and watershed aspect the service is interested in the recognition and control of avalanches endangering ski-ing districts as well as highways and railroads in the Western States.
The work under review, dealing with ten years’ observation of avalanches at Alta in the Wasatch National Park, Utah, is interesting to the outsider rather as indications of the trend of American avalanche research than as a detailed guide on the subject. It refers essentially to local conditions over a small area.
The authors give ten factors responsible for safe or dangerous conditions after a fall of snow:
(1) Old depth of snow, (2) Type of surface, (3) New depth of snow, (4) Type of snowfall, (5) Weight of snow, (6) Rate of fall, (7) Wind force, (8) Wind direction, (9) Temperature, (10) Settlement (inches of settlement per inch of fall).
To this might have been added the humidity of the wind to which reference is made later on in the work, but which the reviewer believes to be of prime importance.
Very detailed analyses of each major snow storm have been compiled and by this method it is claimed that some accuracy can be obtained in forecasting avalanches. The authors recognize that there are, and probably always will be, minor factors of apparently trivial size which may just make the difference between release and non-release of an avalanche. The aim is to bolster experience rather than to enunciate scientific rules and with this approach the reviewer strongly agrees. This work will be studied with profit both by the ski-mountaineer and the theoretical man.
