Page:The National geographic magazine, volume 1.djvu/115

 attached to the Survey, whereby he can anchor the ship in mid-ocean and observe the direction and velocity of the current as from a stationary body, and with a "current meter," also his own invention, determine the same factors hundreds of feet below the surface; thus ascertaining not only the movement at the surface, but the depth of the body of water that moves, and the velocity at various depths, so that finally we have the volume―a quantity―to be followed until it meets other currents or is absorbed in the vast expanse. Already current observations have been recorded with the ship anchored at the great depth of eighteen hundred fathoms; and arrangements have been perfected that it is believed will prove successful at the greater depth of three thousand fathoms. It is impossible with our superficial knowledge of the great ocean currents to estimate the benefits that will be derived from their systematic exploration. It is not probable that the absolute determination of their limits would produce such a revolution in navigation, as was caused by Maury's wind charts, but it is reasonably certain they would prove a valuable assistance to the navigator, and in the great channels and bays of the world increase his facilities for the successful navigation of his ship. Not a little of their value, perhaps the larger part, will be of an indirect nature, resulting from their study by investigators in the natural sciences interested in utilizing the bounties of nature for benefit of man.

The Survey was instituted for the determination of facts, and the presentation of them in an intelligible form. It does not promulgate theories, and has no use for them beyond the assistance they may be in indicating the line of research necessary to ascertain the facts; but rather leaves to the student the formulation of the theories that may be deduced from the facts presented. The publications of the Survey are, therefore, calculated to contain only useful, practical information, on the subjects of which they treat. An examination of them will show this to be the case, and further, that error has more likely been committed by over-caution, than a too free use of the material at command. Doubtless much has been suppressed through lack of means, as it has always been the aim of the Superintendents to expend the appropriations in producing the most useful results, whether in surveys to be made or facts to be published. It necessarily requires many years to complete a precise survey over a large area; and in the work of the Coast Survey, with the people in