National Geographic : 1897 Sep
266 THE COMPASS IN MODERN NA VIGATION deed, it may be said to have come definitely into being with the famous voyage of the Challenger. There had been expeditions for ocean investigation before that, but on a very limited scale. It has only been through the results obtained by the Challenger, supplemented by those of expeditions that have examined more limited areas, that we have been able to obtain an approximate conception of the conditions which prevail throughout the va rious ocean depths-conditions of movement, of temperature, of salinity, of life. We have only a general idea of the contours of the ocean bed, and of the composition of the sediment which covers that bed. The extent of the knowledge thus acquired may be gauged from the fact that it occupies a considerable space in the fifty quarto volumes-the Challenger publications-which it took Dr John Murray twenty years to bring out. What islands are to the ocean, lakes are to the land. It is only recently that these interesting geographical features have received the attention they deserve. Rivers are of not less geographical interest than lakes, and these have also recently been the subject of special investigation by physical geographers. I have already referred to Professor Davis' study of a special English river system. The work in the En glish lake district by Mr Marr, spoken of in connection with Dr Mill's investigations, was mainly on the hydrology of the region. Both in Germany and in Russia special attention is being given to this subject, while in America there is an enormous literature on the Mississippi alone, mainly, no doubt, from the practical standpoint, while the result of much valuable work on the St Lawrence is buried in Canadian official publications. THE COMPASS IN MODERN NAVIGATION By G. W . LITTLEHALES, U. S. Hydrographic Office Transoceanic navigation, with all that it has been to the com merce of the world and the development of the civilization of the nineteenth century, rests upon the magnetic needle of the mari ner's compass. None but those who may estimate the effect of the sudden loss of the earth's magnetism will ever fully know the extent of the influence of the compass in human affairs.