IN referring to the size of the grain of the glacier in the chapter on chemistry and physics in the “Antarctic Manual,” I have given 700 grammes as the maximum weight which I have observed. In August, 1895, I made an extended study of the structure of glacier ice, principally from the Aletsch Glacier. The fragments of this glacier, which float as icebergs in the Mergelin See, are exposed to the powerful weathering influence of the summer sun, and are comparatively easily dissected into their constituent grains. A number of blocks were so dissected in order to ascertain the weight and size of the largest grains. The following weights of single grains were determined:—700, 590, 450, 270, 255, 570, 155 and 100 grammes. It was observed that blocks of ice contained grains of all sizes, which fitted each other so exactly that, in the fresh unweathered block, the whole volume was filled with ice.