PROF. COLE (NATURE, September 12, p. 37) would scarcely maintain the assumption that the stones seen in Boulder Clay were in the “englacial” distribution of the materials in closer juxtaposition than we find them in the deposit itself. The tendency of the larger stones to gravitate towards the bottom of the moving and shearing ice-mass through liquefaction and regelation is well illustrated in the Harlow “till”. But Prof. Cole seems to forget that a conglomerate with an ice-cement would give us a glacial gravel or a “schotter” on the melting of the ice, and not a Boulder Clay. The efficiency as a graving-tool of a grain of quartz or of some harder mineral when caught between the contact-surfaces of two fragments of rock undergoing differential movement can scarcely be doubted.