242 MARINE BIOLOGICAL LABORATORY. 



of their power, however, is found in the temporary re- 

 versal of the regular current of the North Indian Ocean 

 during the period of the southwest monsoon. 



It is not to be wondered at, then, that such a difficult 

 problem as that of the ocean currents presents many 

 dark and unsolved points. If I might suggest a theory, 

 I would say that the winds are the prime mover, setting 

 the current in motion, and all the other factors produce 

 variations or aid this motion and quite likely retard 

 it under the varying conditions in which they are found. 

 The words of Humboldt are almost prophetic in this 

 connection, but I very much doubt whether he had any 

 definite conception of the fulness and completeness of 

 his statement, when he said : " They (the currents) 

 cannot be explained by any one assignable cause ; the 

 phenomena are complicated by the ebb and flow of the 

 tides, the duration and force of the predominating winds, 

 the density and specific gravity of the water, as modi- 

 fied by temperature in different latitudes, seasons, and 

 depths of water." 



Whatever may be their cause, we cannot help but 

 wonder at some of the efforts produced by the constancy 

 and power of these currents. I sometimes think a good 

 way of seeing the benefit of any given order of things 

 is to suppose them reversed. Suppose, for instance, 

 that instead of having this continual circulation in the 

 oceans, keeping every portion in a normal and proper 

 condition for life, and blottino- out all dansfcrous varia- 

 tions, our oceans were stagnant bodies of water. You 

 will instantly recognize the effect which would be pro- 

 duced upon the life of the globe. These great currents 

 have been aptly compared to the veins and arteries 



