The Editor,

The Journal of Glaciology

Sir,

Professor Haefeli’s note on the ogives of the Arolia Glacier (Journal of Glaciology, Vol. 1, No. 9, 1951, p. 498) interested me particularly. Haefeli is correct when he says that the number of such bands is a measure of the number of years for flow of ice over the interval. I checked that on the Mer de Glace last summer; a specially large boulder, which I had noted in 1912, and in 1950, had travelled just 38 bands in 38 years.

Haefeli and Streiff-Becker’s idea that these bands are pressure waves, whose wave length is controlled by seasonal variations in the flow of the glacier, is very interesting. But seasonal variations in flow can only apply to the surface shell of the glacier—the 10 m. shell which alone is penetrated by each winter’s cold wave. With surface ablation of 2 m. or more per annum, the bands at the lower end of his Fig. 1, 30 waves removed, must be in ice which was 60 m. under the surface at their point of origin—a depth far below any penetration of winter cold.

In 1948 on the Arolla and Trift Glaciers (and in 1950 on the Mer de Glace) I verified that the difference in whiteness of the two parts of each band is due to the white band being bubbly ice, the dark band clear ice—densities about 0.85 and 0.91 respectively, rather than to surface dirt. It seems hard to imagine any process by which rhythmic surface compressions could convert clear ice into bubbly ice at the surface; even more difficult 60 m. or more below the surface.

As Henri Bader suggested in the preceding issue of the Journal, I am strongly convinced that bubbly ice is the normal product of fimification of cold snow, with no melt water present. If melt water is present, clear ice results. For instance, the lane of white bubbly ice on the Gomer Glacier can be traced to that cold, arctic, north-facing slope, up against the Silbersattel of Monte Rosa—the one and only large area of Arctic-like accumulation at an altitude of well over 4000 m. in the Alps. That Gomel-white bubbly lane is a longitudinal lane

To introduce transverse dikes of bubbly ice into glaciers such as the Arolla or the Mer de Glace and, at that, dikes of bubbly ice that should penetrate down 100 m. beneath the surface, is one unique test which any explanation of Forbes’s bands must meet (along with others).

Then, too, if nothing more is needed than pressure of a nearby steep ice fall, reacting on a flat glacier whose surface offers rhythmic seasonal fluctuations in its viscosity, as on the Mer de Glace, Arolla and Trift (in the Gothardgebiet), why are there no vestiges of ogives on the Leschaux, below the Talëfre ice fall ? On the Saleinaz ? On the Z’mutt, beneath the Stockje Gletscher ice fall ? On the Gorner, beneath the ice fall coming down from the Jagerhom area? On the Morteratsch beneath its own ice fall—or beneath the Pers Gletscher ice fall?