152 THE PHYSICAL GEOGRAPHY OF THE SEA. 



esis be suggested which will account equally as well, but for a 

 greater number of phenomena. Then, as honest searchers after 

 truth, we should be ready to give up the former, adopt the latter, 

 and to try it until some other better than either of the two be of- 

 fered. 



291. With this understanding, I venture to offer an hypothesis 

 with regard to the agency of the salts or sohd matter of the sea 

 in imparting dynamical force to the waters of the ocean, and to 

 suggest that one of the purposes which, in the grand design, it was 

 probably intended to accomplish by having the sea salt, and not 

 fresh, was to impart to its waters the forces and powers necessary 

 to make their circulation complete. 



In the first place, we do but conjecture when we say that there 

 is a set of currents in the sea by which its waters are conveyed 

 from place to place with regularity, certainty, and order. But 

 this conjecture appears to be founded on reason ; for if we take a 

 sample of water which shall fairly represent, in the proportion of 

 its constituents, the average water of the Pacific Ocean, and ana- 

 lyze it, and if we do the same by a similar sample from the At- 

 lantic, we shall find the analysis of the one to resemble that of the 

 other as closely as though the two samples had been taken from 

 the same bottle after having been well shaken. How, then, shall 

 we account for this, unless upon the supposition that sea water 

 from one part of the world is, in the process of time, brought into 

 contact and mixed up with sea water from all other parts of the 

 world ? Agents, therefore, it w^ould seem, are at work, which 

 shake up the waters of the sea as though they were in a bottle, 

 and which, in the course of time, mingle those that are in one part 

 of the ocean with those that are in another as thoroughly and com- 

 pletely as it is possible for man to do in a vessel of his own con- 

 struction. 



292. This fact, as to uniformity of components, appears to call 

 for the hypothesis that sea water which to-day is in one part of 

 the ocean, will, in the process of time, be found in another part 

 the most remote. It must, therefore, be carried about by cur- 

 rents ; and as these currents have their offices to perform in the 

 terrestrial economy, they probably do not flow by chance, but in 

 obedience to physical laws ; they no doubt, therefore, maintain 

 the order and preserve the harmony which characterize every de- 



