Until the 1950s, British glaciology tended to involve mapping and surveying with simple instruments. From the 1950s onwards, physicists, including Max Perutz, began to focus on the material itself – ice. In the field and in the laboratory (using compression machines) they described mathematically how ice behaves under the stress of its own weight. Other physicists took adapted radar equipment that had been used to explore space, and pointed it downwards at the ice, to measure depth and flow. While these scientists were interested in the ice itself, others were more interested in contaminants, such as lead pollution, and more recently in the bubbles of air in deep cores of ice. It is these air bubbles, rather than the ice itself, that tell us the story of climate change.