of Atmospherical Phanomena, ■ - 299 



which character they retain throughout the rest of the Asiatic 

 continent, even to its eastern coast. In winter the absolute 

 height of the barometer at the northern limit of the monsoon is 

 very great. The still considerable amount of the annual varia- 

 tion at Nangasaki, and the little difference between the curve of 

 Manilla and that of Madras, show that the region in question 

 extends beyond the eastern coast of Asia into the Pacific Ocean ; 

 in higher latitudes, however, its limits appear to be reached in 

 Kamschatka. As the annual variation, which is greater at 

 Madras than at Manilla, is found greater at Aden than at Madras, 

 the western limit of the region would appear to extend far on the 

 African side. 



6. In middle and western Europe the barometric pressure 

 appears to decrease everywhere from the month of January to 

 the spring, usually attaining a minimum in April ; it then rises 

 slowly but steadily to September, and sinks rapidly to November, 

 when it usually reaches a second minimum. In summer, there- 

 fore, the whole atmospheric pressure gains more by increased 

 evaporation than it loses by expansion. This over-compensation 

 is probably, as we have seen above, to be explained by the lateral 

 overflow received in the upper regions from Asia. In Sitka the 

 whole annual curve is convex, a result only found in Europe at 

 considerable mountain elevations, where it is a consequence of 

 the expansion, and extension upwards, of the whole mass of the 

 atmosphere in summer. 



7. The region of great annual barometric variation, on the 

 Asiatic side of the globe where monsoons prevail, extends much 

 further to the north in the northern hemisphere, than it does to 

 the south in the southern hemisphere ; for the variation reaches 

 its maximum at Pekin, while at Hobarton, in nearly a corre- 

 sponding latitude, it has already become inconsiderable ; and it 

 is generally greater in the northern than in the corresponding 

 southern latitudes. The exact contrary is the case on the 

 Atlantic side and in the region of the Trades ; for here the 

 annual variation, though nowhere very considerable, is decidedly 

 greater in the southern than in the northern hemisphere, as is 

 shown by the results of observation at the Cape, Ascension, 

 St. Helena, Rio Janeiro, and Pernambuco, compared with the 

 "West Indian Islands and the southern parts of the United States. 

 Hence it follows, that if we compare places in the same latitude, 

 we find but little difference between the annual variation in the 

 southern Atlantic and southern Indian oceans, while in the 

 northern hemisphere we have in the same latitude the very large 

 annual variation in the north part of the Indian and in the 

 Chinese seas, and the almost entire absence of annual variation 

 in the Atlantic (compare Chusan with the Azores and Madeira). 



