Within the Periods there is a still more limited kind of geological division, founded upon the special character of local deposits. These I would call geological Formations, indicating concrete local deposits, having no cosmic character, but circumscribed within comparatively narrow areas, as distinguished from the other terms, Ages, Epochs, Periods, which have a more universal meaning, and are, as it were, cosmopolitan in their application. Let me illustrate my meaning by some formations of the present time. The accumulations along the coast of Florida are composed chiefly of coral sand, mixed of course with the remains of the animals belonging to that locality; those along the coast of the Southern States consist principally of loam, which the rivers bring down from their swamps and low, muddy grounds; those upon the shores of the Middle States are made up of clay from the disintegration of the eastern slopes of the Alleghanies; while those farther north, along our own coast, are mostly formed of sand from the New-England granites. Such deposits are the local work of one period, containing the organic remains belonging to the time and place. From the geological point of view, I would call them Formations; from the naturalist's point of view, I would call them Zooelogical Provinces. Of course, in urging the application of these names, I do not intend to assume any dictatorship in the matter of geological nomenclature. But I do feel very strongly the confusion arising from an indiscriminate use of terms, and that, whatever names be selected as most appropriate or descriptive for these divisions, geologists should agree to use them in the same sense. There is one other geological term, bequeathed to us by a great authority, and which cannot be changed for the better: I mean that of Geological Horizon, applied by Humboldt to the whole extent of any one geological division,--as, for instance, the Silurian horizon, including the whole extent of the Silurian epoch. It indicates one level in time, as the horizon which limits our view indicates the farthest extension of the plain on which we stand in space. * * * * *