In Moliere's comedy Le Bourgeois Gentilhomme, the hero M. Jourdain spoke in prose without knowing it. In the nineteenth century the inhabitants of high mountains of the French Alps were engaged in “applied glaciology” also without knowing it. Allow me to recall as introduction to my paper a few instances concerning some of the main problems which have been reported during the last century.

In the second part of the nineteenth century during the great adventure of building railways, one of the most impressive projects was the construction of a cog-railway all the way to the top of Mont Blanc. This project involved a study by Vallot which was the first systematic study of thickness of the ice cap on the top of Mt Blanc. The picture shows that the railway followed the areas where the ice was absent or of minimum thickness. It was in fact very important to make the tunnels so that they did not come into contact with the ice, but stayed in the rock all the time. The project was not completed except for one part between 1000 and 3000 m; but the glaciological research was done!

In 1892 a subglacial water pocket of more than l00000 m³ broke out from the small glacier of Tete Rousse killing 175 people in the valley below and destroying the thermal establishment of St Gervais. Therefore the Administration des Eaux et Forets took preventive action and constructed a tunnel through the rock in order to empty other possible water pockets so that they should not cause any further destruction. This was one of the first projects in subglacial hydrology.

In this period one could use ice from glaciers to fill up ice boxes in restaurants and in butcher's shops. The main problem was how to preserve the ice. This was done by means of sawdust, straw, and also snow.

Another problem that was present for mountaineers was how to build and protect mountain huts near or on the glaciers. The problem still exists: the refuge du Gouter would not survive if great volumes of ice were not dug out every year at the cost of some $2 000 per year. The observatory built by Vallot was subject to great ice pressures and had to be taken down and rebuilt on an isolated rock knob. It has remained there since the beginning of the century. Janssen built his observatory on the very top of Mt Blanc. Because of the annual snow accumulation of 1 m per year the seven-metres-high building constructed in 1893 had completely disappeared in 1908.

Today the need for applied glaciology in the Alps is of course much greater and there can be a mutual exchange of information: The glaciologist should really take an active part in the exploitation of the mountains particularly for the sake of safety, forecasting work and hydroelectric plans. On the other hand the planners of mountain resorts will be able to let the glaciologists collect information from places not normally available.

I would like to give a few examples of projects that we have carried out in connection with recent developments during the last few years.

At the Glacier de la Grande Motte a cableway station was built on rock below the summit at an altitude of 3453 m. One part of the station had to be cut into the ice and this has caused certain problems because of the ice pressure. We have found that the stagnant ice around the station has a diverging flow with a speed of 4 to 10 m per year. The next step will be to measure pressures on the station walls and to propose what action will be taken in the future. One could think of a concrete wall splitting the ice flow or perhaps putting up large mirrors along the walls in order to melt the ice and snow around the station.

The problem is quite different at the Glacier d'Argentière. The glacier is growing in thickness and sometimes the cable car passing over it hits the ice and a trench has to be dug out with a pick to permit the passage. Here some work has been done to study the lateral advance of the glacier. Another problem is that the glacier, advancing laterally (3 cm per day) is now threatening one of the pylons. The ice is about 30 m high and the pylon is 17 m: that prevents the construction of any protection walls. The solution has been to melt the ice with a system of hot water.

To melt basal ice, Electricite de France have developed equipment with which they can spray warm water at a temperature of 35°C and can make under the glacier a tunnel 2 m high and 1.5 m wide at a rate of 8 to 9 m per day which corresponds to the melting of 1.1 m³ of ice per hour.

On the Glacier de Chavière the preparation of ski runs and the construction of ski-lifts for summer ski-ing has caused certain problems. We had to know the movement conditions of the glacier, particularly the monthly variations, in order to adjust the constructions on the ice surface. One also has to know where the crevasses are, to be able to limit the safe areas for ski-ing. For the study of the movement we survey a system of stakes. We also use a Flotron camera system which gives us the daily movement.

In order to detect the different snow structures and the crevasses we have experimented with several different films, filters, and false colour; we worked in the visible part of the spectrum and in the near infra-red. On the pictures of the studied area taken with the normal Ektachrome 64 film with an ultra-violet filter it is difficult to see anything except the white snow surface. On the picture taken with infra-red film and a Wratten 12 filter one can distinguish more snow features which allow us to map the surface of the glacier. The same can be said about the picture with infra-red film and an ultra-violet filter. The best results are obtained with infra-red film and a Wratten 87 filter, which eliminates the visible radiations.

One can then see crevasses which are still hidden under snow: they appear as black lines. The second kind of applied glaciology concerns situations where new opportunities created by human activity near, on, or in the glaciers help glaciologists to make observations of features which have never before been available for study.

The best-known examples are connected with construction works for the hydroelectric companies. They want to catch the subglacial waters and in the tunnels constructed for this purpose in the last 10 years glaciologists have had wonderful opportunities to study plasticity of ice, subglacial cavitation characteristics of the basal ice, and the associated subglacial drainage.