1837-3 the South African Literary and Scientific Institution. 399 



noticed, as he at that time supposed for the first time, but which it 

 appears had also been (ve^y recently) noticed and made the subject of 

 inquiry and numerical computation by Professor Schow ot' Copenhagen, 

 in a paper published in the Annales de Chimie for June 1833. 



Sir J. Herschel also farther slated, that the mean annual barometrie 

 fluctuation at Calcutta, on the average of between two and three years' 

 observations made by Mr. Prinsep, examined by him, appears to be 

 much greater than that at the Cape, and, what is very remarkable, in a 

 contrary direction, the maximum of Calcutta corresponding to the 

 minimum at the Cape. And he attributes this to an actual bodily 

 transfer of a portion of air from hemisphere to hemisphere, by the 

 alternate heating and cooling of the two hemispheres, as the sun 

 crosses from side to side of the equator. The effect of this cause, 

 which he considers to be general over the whole earth, will be to modify 

 the regular and constant effects of the Trades, by a set of periodical 

 winds differing materially in their character from local monsoons, and 

 to this cause he is disposed to attribute the observed annual oscillation 

 of the extreme north and south limits of the Trade winds. 



The northern hemisphere, he further observed, being, by reason of 

 its greater quantity of land, more superficially heated than the southern, 

 it should be expected that the mean pressure beyond the southern 

 tropic should exceed that beyond the northern, and he suggested this 

 as a subject worthy of examination by meteorologists properly situated 

 in both hemispheres. •> 



Lastly, h*? observed, that severe gales, occurring whether in summer 

 or winter, appear to depend on causes entirely extraneous to the regular 

 periodical fluctuations of pressure, and are probably dependent on 

 causes of a local and transient nature — but that a correspondence of 

 extraordinary seasons in distant parts of the globe, may be expected to 

 accompany great occasional deviations from the usual law of these 

 fluctuations in any given place, and that it is far from impossible that 

 an assiduous attention to this point may ultimately enable us to predict 

 their occurrence. 



The series of observations at the Port-Office being still in progress 

 the foregoing results are not considered as final ; but whatever modifi- 

 cations future years' observations may necessitate, will be from time to 

 time inquired into and reported. — Edinburgh New Philosophical Jour- 

 nal for July — October 1836. 



