The author, after briefly stating the views of Mr Milne, and the remarks of Sir G. S. Mackenzie, gave his reasons for agreeing with the former, that the terraces were the beaches of lakes, formed by barriers across the valleys; and, with the latter, in holding that these barriers could not have been formed of earthy detritus. He then proceeded to shew that the theory of Agassiz, according to which the barriers were formed of glaciers, was the most probable yet advanced, and while it required some modification in the details to render it consistent with recently observed facts, was strongly supported by the researches of Professor Forbes, both in regard to the former existence of glaciers in our latitudes, as demonstrated in the case of the Cuchullin Hills, and in regard to the laws of the motion of glaciers, as developed in Professor Forbes's papers on the Glaciers of the Alps.