246 MR. THOMAS HOPKINS ON THE INFLUENCE 



XVII. — On the Influence of the Earth^s Rotation on Winds. 

 By Thomas Hopkins, Esq., M.B.M.S. 



Eead December i6th, 1862. 



Great importance has been given by many writers to the 

 effects that are said to be produced by the unequal rota- 

 tory velocities of different latitudes on the winds that 

 pass over the surface of the globe. It has been confidently 

 asserted that winds passing from the northern polar re- 

 gions take with them only the slow rotatory movements of 

 the latitudes from which they are passing, and are there- 

 fore palpably left behind by the quicker rotating surfaces 

 of more southern parts, converting a north into a north- 

 east wind. A wind from the southern polar regions is 

 said, in like manner, to be converted into a south-east 

 wind. The great trade- winds of the tropics are stated to 

 be, in this way, changed from north and south into north- 

 east and south-east winds. That air, passing from polar 

 to tropical regions, is affected, to some extent, in this way 

 is admitted ; but the extent has been greatly exaggerated, 

 apparently in order to support an imaginary theory of the 

 tropical trade- winds. 



The atmosphere presses on the surface of the globe with 

 a force equal to about 15 lbs. weight on every square inch, 

 and by that pressure it appears to be made to adhere so 

 strongly to it as to enable the surface readily to take with 

 it the air that is in the part at about its own velocity in 

 every latitude. But if such an effect as that which has 

 been alleged is produced by the cause named to a palpable 

 extent, we might reasonably expect to find it in operation 

 over the whole globe when air is in motion upon it ; we 

 may therefore inquire whether that is or is not the case. 



