B. TERRESTRIAL PHYSICS AND METEOROLOGY. 65 



B. TERRESTRIAL PHYSICS AND METEOROLOGY. 



MECHANICAL THEORY OF OCEAN CURRENTS. 



The application of mathematics and the laws of mechanics 

 to the theoretical investigations of the currents of the at- 

 mosphere and the ocean, with w'hich subject American stu- 

 dents have become so familiar through the labors of Professor 

 Ferrel, has of late years been taken up quite energetically 

 in Europe ; and to the labors of Colding, Peslin, Everett, 

 Thomson, Hann, and others, we now have to add the some- 

 what elementary memoir of Professor Blazek on the elements 

 of a mechanical theory of the ocean currents, which com- 

 munication is, he implies, introductory to a more extended 

 memoir that may be expected from him. He considers that 

 every particle of water is actuated by two forces that of 

 gravity toward the centre of the earth, and the centrifugal 

 force due to the daily rotation of the earth. The centrif- 

 ugal force in and of itself can produce no constant current, 

 since it is in obedience to it that the earth owes its perma- 

 nent ellipsoidal shape ; but if on such an ellipsoid the tem- 

 perature in general diminishes toward the equator and toward 

 the two poles, there results a tendency toward a new dis- 

 tribution of the mass of the water, which therefore demands 

 a new figure of equilibrium. The dense, cold waters of the 

 two polar seas, therefore, flow toward the equator, while the 

 lighter warm waters flow from the equator toward either 

 pole. Less water flows from regions of low temperature to- 

 ward the regions of high temperature, and the northern hem- 

 isphere sends to the equator less cold water than the southern 

 hemisphere. Consequently, as he demonstrates, the centres 

 of all the closed portions of the equatorial currents in all 

 oceans are found between the 35th and 30th parallel of lati- 

 tude. The centrifugal force drives the cold water toward 

 the equator and the warm water toward the polar regions, 

 and in consequence of the earth's rotation these latitudinal 

 currents are turned aside those from the poles to the west, 

 and those from the equator to the east. Sltzh. K. Bohm. 

 GeselL, 1874, 195. 



