THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



FEBRUARY 1870. 



XII. On Ocean-currents. By James Croll, of the Geological 

 Survey of Scotland*. 



Part I. 



Ocean-currents in relation to the Distribution of Heat over the Globe. 

 r i^HE absolute Heating-power of Ocean-currents. — There is 

 perhaps no physical agent concerned in the distribution 

 of heat over the surface of the globe whose influence has been 

 so much underrated as that of ocean-currents. This is no doubt 

 owing to the fact that although a considerable amount of atten- 

 tion has been bestowed in ascertaining the surface-temperature, 

 direction, and general influence of ocean-currents, still little or 

 nothing has been done in the way of determining the absolute 

 amount of heat or of cold conveyed by them, or the absolute in- 

 crease or decrease of temperature, as the case may be, which 

 must result from the heat or cold conveyed. 



The modern method of determining the amount of heat -effects 

 in absolute measure is, no doubt, destined to cast new light on all 

 questions connected with climate, as it has done and is still doing 

 in every department of physics where energy, under the form of 

 heat, is the phenomenon under consideration. But this method 

 has scarcely been attempted yet in questions of meteorology; 

 and owing to the complicated nature of the phenomena with 

 which the meteorologist has generally to deal, its application 

 will very often be found practically impossible. Nevertheless it 

 is particularly suitable to all questions regarding the direct 

 thermal effects of currents, whatever the nature of those currents 

 may happen to be. 



* Communicated by the Author. 



Phil. Mag. S. 4. Vol. 39. No. 259. Feb. 1870. G 



