OCEANIC CIRCULATION. 241 



Pacific submarine circulation (if Dr. Carpenter's theory 

 be true), as well as that of the North Atlantic, we can 

 scarcely doubt, as it seems to me, which cause is the 

 more effective. I would venture to predict that if 

 Dr. Carpenter's experiment were tried first with the 

 ice alone to produce circulation, and secondly with the 

 heat alone, the superior efficiency of the latter cause 

 would be at once recognised ; but I much more confi- 

 dently predict that if, as in the experiment I myself 

 proposed, the relative areas of the equatorial and arctic 

 basins were represented, there would be found to be 

 scarcely any comparison between the effects of arctic 

 cold and equatorial heat, so largely would the latter 

 predominate. 



It is necessary to mention, however, that the prin- 

 ciple itself of the experiment has been objected to, on 

 the ground that the gradation of temperature must 

 always be much more rapid in such an experiment 

 than in the actual case of the Atlantic Ocean. This 

 objection, however, is, in rea)ity, based on a misappre- 

 hension. It is sufficient that the difference of tem- 

 perature at the two ends of the trough should corre- 

 spond to the difference between the temperature of the 

 arctic and equatorial seas ; and it is a matter of no im- 

 portance whatever that the real rate of gradation should 

 be represented. The case may be compared to the 

 illustration of the descent of water to form springs or 

 the like. Here an experiment would be valid in which 

 the outflow of the illustrative spring was obtained by 

 causing the vent to be so much below the level of the 



