In August, 1841, Professor J. D. Forbes, in company with Professor Agassiz and Mr. Heath, spent some time upon the Lower Glacier of the Aar, and Forbes states that it was then for the first time that he noticed the veined or ribboned structure of glaciers. Although the description given in the communication he made to the Royal Society of Edinburgh in December of the same year is most interesting, he does not state clearly how the structure is related to the glacier grains of which the ice streams are built up.