The publication by the Royal Society of Edinburgh in 1890 of the hourly observations made at the observatory on the summit of Ben Nevis along with corresponding observations at five different hours at Fort-William at the sea level was an important contribution to meteorological science. As I held at the time the Lectureship in Geography at the University of Cambridge it furnished a welcome supply of facts for the illustration of important points in physical geography. What struck me most at the time in the study of this work was the unique character of the observatory of Ben Nevis itself, without reference to its companion at the sea level, as a first-class observatory in a locality where the atmosphere is for the greater part of the year completely saturated with moisture. Being also situated on a true peak, and that the highest point in the British Islands, the observations may fairly be taken to represent the meteorology of the clouds, or at least of such clouds as are in contact with mountain slopes, and in any case they must afford rich material for the study of the physics of the atmosphere.