Henry Osmaston

Henry Osmaston came into one of our first glaciology lectures at Bristol with a sheaf of dog-eared notes and a large test-tube stand, writes Martin Sugarman [further to the obituary by Stephen Venables, 10 July]. He took from his pocket a tennis-ball-sized lump of grey putty which he proceeded to roll and bounce - alternately - on the lecture desk as he spoke. Continuing his narrative, as though this kind of demonstration was quite normal, he nonchalantly stuck the ball to the test-tube stand. Slowly, the gunge began to droop and elongate in a rather suggestive manner, as our giggling gradually climaxed into howls of laughter. He then suddenly stopped and suggested that we might be wondering - to more laughter - about the extenuated blob: the movement of the "putty", he explained, was directly analogous to the way ice moves downhill in a glacier.

In the days before videos and animated aids, never has a scientific point been made with more humour and clarity.

His utter imperturbability was demonstrated on a field trip in South Wales. He took a group of us to the edge of a stream. In his reassuring, clipped English accent, he urged us - officer-style - that it was quite safe to cross here; then confidently stepped out into the stream and disappeared up to his shoulders in the swirling waters. Clambering out, dripping wet but totally unfazed, he declared that this was a good example of how deceptively deep limestone river potholes could be as a result of physical and chemical erosion. He then strolled off to continue our walk.

My abiding memory of Henry Osmaston, writes Richard Hall, is his striding up to a tree and giving it a Zidanesque head-butt, to the horror of the accompanying students. It transpired that the tree was a redwood, renowned for its spongy bark. I have been impressing friends with this trick for 20-odd years since.