Sir,
It happens rather often that former glaciological work has been done in vain because succeeding explorers do not know about it. This is particularly bad in cases when such things as special glacier maps remain unknown, which could provide valuable information and data for following studies.
The seismic investigations at Zemu Glacier, Sikkim, (Reference BoseBose and others, 1971) may be an example. The authors have carefully studied and used the work of several predecessors, but have obviously not known and therefore not used the glacier map of the Zemu which has been published together with a detailed article on the same glacier (Reference WienWien, 1933). The map shows the state of the glacier in 1931 and, together with other data in the article, can be compared with the results of the recent work. To give an example: the seismic cross-section measured in 1965 could be studied together with the velocity profiles across the glacier measured by photogrammetry in 1931 at altitudes of 5 250 and 4 600 m, the latter rather near the recent seismic section at 4 500 m. The ice depth of 310 m at this section (Reference BoseBose and others, 1971, fig 9, p. 119) shows that the thickness of 220 m which Reference Finsterwalder and BauerFinsterwalder (1933) computed by using Somigliana’s and Lagally’s formula for a place higher up and nearer the equilibrium line (at about 5 400 m) is probably much too small. This is another example of the fact which has become well known in the meantime, that the ice depth cannot be determined from values of the surface velocities.
Perhaps a bibliography of glacier maps and other existing data arranged in a geographical order could change the present unsatisfactory situation, as a result of which valuable glaciological work remains unused. Such a bibliography could be confined to remote regions where literature is obviously difficult to discover and to obtain. It should contain old reports, papers, sketches, pictures, and maps, together with complete references and short notes about the information which can be expected. Such a survey on former literature would be a valuable contribution to the IHD.
