More than sixty years have elapsed since Linde first liquefied air on a commercial scale and prepared the way for separating of other gaseous mixtures. His work, however, was not of an isolated nature. It was conceived eighteen years after air had, for the first time, been liquefied in the laboratory by Pictet in Geneva and Caillete in Paris. Linde's liquefaction of air was followed by Dewar's work on hydrogen liquefaction in London and by the setting...