Detailed information on subglacial conditions is clearly a fundámental necessity for the advance of scientific glaciology. It is most desirable, therefore, to publish as many details as possible of available techniques of glacier sounding, and the relative success of these. There has been very considerable activity in this field in connexion with recent hydrological surveys in Europe, particularly in France and Switzerland, and reports on glacier soundings from these countries are, therefore, especially welcome. Both of the above papers include discussions of the theoretical backgrounds and development of the techniques used, together with some details of recent work. In the case of the Swiss glaciers the seismic method was employed, on the French glaciers thermal borings were also used.

It is clear that most valuable results have been obtained. Of those already published the detailed cross-section of the Mer de Glace, showing a V-shaped profile very different from that which would be expected according to orthodox views, will perhaps be of particular interest to glaciologists. We must be grateful that in many instances the glaciers investigated by the hydrological commissions have been the same as those of which many other studies have already been made. The new results are of so much the greater value to us.

It would appear that the writers of the papers are, on the whole, conversant only with Continental sources, and although Renaud and Mercanton mention the work of Perutz in 1948 on thermal soundings, Bourgin is clearly unaware that the method was developed quite independently by Perutz and Gerrard. However, such lack of contact must of necessity disappear with the publication of papers such as these.