of Atmospherical Phenomena. 35 
ture, the air expands, and by reason of its augmented volume 
rises higher and at its upper portion overflows laterally,—while 
at the same time the increased temperature catises increasing 
m=) 
iu the atmosphere,—so it naturally follows that the composite 
result in the periodical variations of the barometric pressure 
relation to the periodical changes of temperature. It is only 
when we know the relative proportions of the two variations 
which take place in opposite directions that we can determine 
whether their joint effect will be an increase or a decrease with 
increasing temperature,—whether in part of the period the one 
variation may preponderate and in other parts the other variation. 
The following are the results which we are enabled to derive 
from observation. 
5. Throughout Asia, the increase in the elasticity of the aque- 
ous vapor with increasing heat is never suflicient to compensate 
the diminished pressure of the. dry air, and the annual variation 
of barometric pressure is therefore every where represented in ac- 
cordance with the variation of the pressure of the dry air, by a 
simple concave curve having its lowest part or minimum in July. 
The observations in Taimyr Land, at Iakousk, Udskoi and 
Aiansk, show that this is true up to the Icy Sea on the north, 
and to the sea of Ochotsk on the east. On the west a tendency 
towards these conditions begins to be perceived in European 
Russia in the meridian of St. Petersburg, and becomes more 
marked as the range of the Uyal is approached. On the Caspian 
and in the Caucasus the phenomenon is already very distinctly 
marked ; its limit runs south from the western shore of the Black 
Sea, so that Syria, Egypt and Abyssinia fall within the region 
Over which it prevails. Towards the confines of Europe there 
by a slighter inflexion or secondary minimum; it is only beyond 
the Ural that the curves become uniformly concave, with a single 
summer minimum and winter maximum, which character they 
retain throughout the rest of the Asiatic continent, even to its 
€astern coast. In winter the absolute height of the barometer at 
the northern limit of the monsoon is very great. The still a: 
Siderable amount of the annual variations at Nangasaki, and 
the little difference between the curve of Manilla and that 
f Madras, show that the region in question extends beyond the 
astern 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 an at Madras, the western limit of the 
region would appear to extend far on the African side. 
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