Besides mathematics, Georges de Rham was also passionate about the problems posed by mountaineering, in the most difficult routes as well as in research and attack new routes: he had found in the Alps his playing field. From the late thirties and through almost a decade, I had the good fortune to make with him many climbs in the Valais Alps and in the Vaud Alps, or the North Slope of the Argentine. What struck me during particularly difficult climb was his extreme agility and sometimes even his audacity, contrasting with calm and thoughtful attitude. The more precarious the conditions became, the more he seemed to dominate the situation, naturally imposing his authority: in critical moments, he seemed to me to have amazing mental and physical resources.

Let me begin by describing an encounter which took place in September 1926 at the Refuge de la Charpona, a climbing hut high above the Mer de Glace near Chamonix. Two parties of two were both planning to traverse the Aiguilles des Drus, but in opposite directions. They agreed to leave their ice axes at the edge of the glacier where their respective rock climbs began, so that each party could avoid the awkwardness of carrying axes on the rock, but would have them waiting for the descent. Everything went as planned: the two parties crossed near the summit, picked up the waiting ice axes on the way down, and recovered their own axes when they returned to the refuge that evening, without ever introducing themselves. A few years later one of the climbers, Georges de Rham, happened to run into a member of the other party, a well-known musician, and asked who his companion had been. He discovered that it was James Alexander, whose mathematical work he knew well. De Rham met Alexander again in 1932, at the International Congress in Zurich. Then in 1933, near the Weisshorn in Valsis, de Rham encountered Alexander who was climbing with Hassler Whitney. This meeting was the beginning of a long friendship between Whitney and de Rham, who visited our climber together frequently for more than forty years.

I first went rock climbing with Georges de Rham in the 1960s, on the Salève near Geneva, I was rather apprehensive about climbing with such an old person. He walked very deliberately, keeping careful track of his pulse as we went up the trail. However, once we started actually climbing, he was flying up the rock and I was worried only about myself. I have particularly fond memories of climbing with Georges on the Argentine, a mountain with lovely silvery walls in his home Canton of Vaud, and I can remember a fine day there with Georges and with Hass, followed by a delicious raclette in the little village of Solalex. I also have happy memories of a topology conference which was held some years later in the nearby village of Les Plans sur Bex, high in the mountains of the Vaud. This area was very special to Georges; and I treasure a copy of the guidebook to the Argentine which he wrote.

... my most vivid memory is of a climb of the south ridge of the Baltschieder Stockhorn in northern Valais in 1966, with Georges together with Oscar Burlet and Jacques Boéchat. This was long and steep, a series of five stepped towers, with excellent rock almost too exciting for me. (I probably learned more French that day than I have in the rest of my life: There is nothing that focuses the mind so much as a little terror.) Starting out at dawn, I assumed that we would return by daylight, and brought only dark glasses. But by the time we got to the foot of the formidable fifth tower, it was already well after noon. I was overwhelmed, and ready to give up and go back; but Georges explained to me that it was too late - it would be much safer to go ahead and return by the relatively easy east ridge that to try to retrace our steps. We got over the crux of the climb, an overhang with what seemed like miles of air under our feet, with the aid of a small rope ladder. It was pitch dark when I stumbled down the trail at the end of the day, still wearing my sun glasses, but very happy.

I remember in particular the ascent of the Baltschieder Stockhorn by the south ridge in summer 1966. There was a symposium in Geneva in honour of de Rham, which involved John Milnor, a famous American mathematician who loved the mountains and had already done some climbing. George suggested to Boéchat, Milnor and myself, that we take the south ridge of the Stockhorn. He had made the first ascent on 17 June 1945 along with eight other climbers from Geneva and Vaud. This is the description so that F Marulaz gives in the Bernese Alps Guide:

The south ridge of the Stockhorn, 600-700 metres high, is a succession of bold towers separated by more or less deep gullies. The 2nd, 3rd and 4th towers, roughly equal in altitude, exceed the first by one hundred metres. The fifth tower, which has an impressive vertical face of 150 metres, is the most difficult part of this beautiful climb .... The climb, sustained and very difficult on beautiful granite, requires rubber-soled shoes.

The idea of this route enchants us and one morning we start from Lausanne to reach the bivouac at Martischüpfe in the beautiful and wild Baltschieder Valley. A furnished chamber under a huge granite slab serves as our refuge. Lulled by the roar of the nearby river we spend the night there. Early morning departure, around 4:00, is on the path of the Baltschiederklause, we soon leave path for a straightened and a little appealing corridor that leads us from our track. We are roped in pairs, Boéchat and Milnor, and de Rham and me. Climbing is wonderful, the solid rock, the splendid weather. But the hours pass, all these towers to climb and abseil back down with manoeuvres on the rope. It was not until 13:00 we reach the gully that gives us access to the fifth round. We are hanging, with precipices to the left and right, behind us the 4th tower we have just abseiled down and before us the 5th tower, huge, daunting. Then George explains the different possibilities to get through, one consisting of making a pendulum and the other to go straight but moving very delicately. There, Milnor broke down. He did not want to continue. After hours of climbing that had tested him to the limit, given his training, the view of the tower and the prospect of the climb was too much. But to descend four at a time from the gully would be dangerous and we would never arrive before nightfall, we would be left unable to continue. Then, George intervenes. He comforts Milnor but firmly makes him understand that it is impossible that we should descend and it is necessary to go over the top. Finally, after fairly steady climbing, we reach the top at 17:00. It's late and we are left with going all the way down the east ridge. The terrain is easy, we can walk together, but the ridge is long. Georges constantly spurs us on, but it is around 21:00 when we get back down to Martischüpfe. There we spend a second night and the next day it's back in Lausanne. It was really amazing to see the stamina and resources Georges had during this climb. Let us not forget that he was over sixty years of age at the time and that we, much younger people, were feeling absolutely shattered.

1918. On 8 September, de Rham, climbed to the summit of the Diablerets massif (3210 m), on a trip from Aigle through the Pillon pass to Anzeinde, together with his father and his brothers.

1920. In August, climbed the Grand Combin (4314 m), on a trip from Valsorey to Panossière.

1923. First ascent of the west face of the Pacheu, together with R von der Mühll. This is the beginning of a long series of first ascents in the Alps.

From 1930. "Through the years 1930 to 1960, G de Rham was a very active mountaineer, one of the best in Switzerland."

1944. Monograph on the Argentine, limestone face in the Vaud Alps. Mountaineers today see this as an important date, because "The author, in using descriptive words in a very precise sense, manages to describe accurately the difficulty of each climb. Remarkable insight for time.

1973. Ascent of the Grand Combin by the Meitin ridge. At the summit, G de Rham remarks that he is celebrating the 53rd anniversary of his "First Grand Combin."