In presenting to the National Geographic Society this first annual summary of work accomplished in the domain of the Geography of the Sea, I find it impossible satisfactorily to limit the range of subjects that may be assigned to it. The great ocean is so large a factor in the operations of Nature, that the attempt to describe one of its features speedily involves the consideration of others lying more or less in that shadowy region which may be claimed with equal force by other sections of the Society. It is to be understood, therefore, that the following account merely touches upon several of the characteristics of the oceanic waters, and is not in any sense an attempt to treat them all. This being the first report to the Society it has been thought advisable to give a brief outline of the progress made in our knowledge of the sea since 1749, when Ellis reported depths of 650 and 891 fathoms off the north-west coast of Africa. Even at that time an apparatus was employed to lift water from different depths in order to ascertain its temperature. It does not appear that this achievement gave impetus to further efforts in this direction, for, except some comparatively small depths and a few temperatures recorded by Cook and Forster in their voyage around the world in 1772-75, and in 1773 by Phipps in the Arctic, at the close of the last century there was but little known of the physical conditions of the sea. At the beginning of the present century, however, more activity was shown by several governments, and expeditions sent out by France, England and Russia, in various directions, began to lay the foundation of the science of Oceanography. Exploration of little known regions was the main purpose of most of these expeditions, but attention was paid also to the observation and investigation of oceanic conditions, so that accounts of soundings, temperatures of sea water at various depths, its salinity and specific gravity, the drift of currents, etc., form part of their records.