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 b}^ 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, 

 TJ. 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 eff'ect of 

 the sudden loss of the earth's magnetism will ever fully know 

 the extent of the influence of the compass in human affairs. 



