SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 475 



observation ; and it is easy to assure ourselves that this is, in general,, 

 very satisfactory. 



But we ought not to conceal the fact that some discordances jiresent 

 themselves when we enter into details ; that our theory does not explain 

 certain observations of the force and direction of the wind recorded 

 in the atlas. These exceptional facts, it seems to us, ought to be ex- 

 plained either by local influences, such as the attraction of coasts, of 

 valleys, of mountains, or by periodical or accidental meteorological 

 phenomena, such as the morning breezes, gusts of wind, thunder-storms, 

 &c. The proportion of discordances to the accordances is too small to 

 throw any doubt upon the exactness of the theorj\ 



(9) Application of the same Theory to Ocean Currents. 



I will terminate this memoir by an application which does not directly 

 refer to meteorological i^henomena, but which has a certain interest in 

 reference to the general physics of the globe. Let us consider a grand 

 ocean current, as for example, the Gulf Stream along the coast of North 

 America. A particle of the surface moving with the velocity V is sub- 

 ject to two forces: gravitation, a vertical force whose intensity isw^, 

 and the composite centrifugal force, a horizontal force whose direction is 

 normal to that of the current, and whose intensity is mF = 2 m V Q> sin X. 

 In order that the particle of water should not deviate, but continue to 

 progress in the same direction with the same velocity F, it is necessary 

 that the free surface of the sea should be, at this ])lace, not horizontal 

 but normal to the resultant of the forces m g and m F', that is to say, 

 that in a section taken normal to the direction of the current the free 

 surface presents an inclination, /, to the horizontal plane whose value 

 satisfies the equation 



tangi = =2 —Fsin X. 



mg g 



Thus, in the same way that the trade-winds and the auti trades are 

 the cause of the increase in the barometric pressure toward parallels 30<^, 

 in precisely the same way the Gulf Stream, which reproduces at the sur- 

 face of the sea the circulation of the general currents of the atmosphere, 

 gives rise to an elevation of the level of the sea at the center of the 

 Atlantic, or to an accumulation of water in the region about which the 

 current circulates. Let us calculate the inclination Zand the difl'ereuce 

 of level to which this inclination gives rise. 



If in the formula which gives tang I are substituted the values of 



a = 9^.8088 and of Q = ?-^^-5^Ml^, 

 •^ 804UU ' 



"we obtain 



whence — 



I = 3".06 V sin X. 



