OSCILLATIONS OF THE BAROMETER. 37 



opinion. But this is absolutely at variance with the 

 theory suggested in our preceding volume: accord- 

 ing to which the westward pressure of that upper 

 strata is the greatest wind-creating power in the 

 atmosphere ; and according to which, with the excep- 

 tion of comparatively trivial counter-currents, and 

 the exterior limits of the trade winds where the air 

 from the upper strata curves eastwards in descending 

 into the lower strata; with these exceptions, the 

 tendency of the whole mass of air in the equatorial 

 regions is westwards : that in the lower strata con- 

 verging towards the equator, and that in the upper 

 strata diverging from the equator. The exceptional 

 direction taken periodically by the monsoons in the 

 lower strata must necessarily result from the influ- 

 ence of change of latitude whenever the trade wind 

 of one hemisphere is carried any considerable distance 

 across the equator into the opposite hemisphere, and 

 is therefore no argument against the wind-creating 

 action of the westward pressure of the equatorial 

 regions. Dove has ably shown, and we believe first 

 suggested, that these monsoons are simply extensions 

 of the trade winds. But this eastward sweep of the 

 trade wind, which periodically forms the monsoons, 

 must, according to our theory, be confined to the 

 lower strata : the air above in the upper strata, with 

 the trivial exceptions above mentioned, running con- 

 stantly westwards. 



