130 Philosophy of Storms. 
will cause the air to run in below towards the equator, and of 
course rise there. Now from the principle of the conservation of 
areas, it will fall more and more to the west as it rises, and of 
course the upper current of the 26 at the equator probably moves 
towards the west. 
However, as the air rolls off above, towards the north, it will 
be constantly passing over portions of the earth’s surface, which 
have a less diurnal velocity than the part from which it set out, 
and as from the nature of inertia it still inclines to retain the: di- 
urnal velocity towards the east which it originally possessed, 
when it reaches the latitude of about 20° or 25°, it will then pro- 
bably be moving nearly towards the north—and beyond that lat- 
itude its motion will be to the northeasterly. 
If violent storm clouds, which necessarily rise to a great height 
into the upper current, are driven forward in the direction of the 
upper current, it is probable that the barometer will rise higher in _ 
that part of the annulus which is in front of the storm, than in 
the rear, and if so, a sudden rise of the barometer in particular 
localities, may become, when properly understood, one of the first 
symptoms of an approaching storm. 
In consequence of the high barometer in front of the storm in 
a semi-annulus, the air will be forced downwards there, and 
cause in some Cases a more violent action of the air or wind 
backwards, meeting the approaching storm, mm will be experi- 
enced, in the rear of the storm. 
As the air comes downwards in the semi-annulus in front of 
the storm, it will come under greater pressure, and therefore any 
clouds which it may contain, will probably be dissolved, by the 
heat of greater pressure, and therefore on the passage of the annu- 
lus, it will probably be fair weather. 
Also, as the air above always contains more caloric to the 
pound, than the air below, there will be an increase of tempera- 
ture on the passage of the annulus, partly from the increased 
pressure, but chiefly by the descent of the air; in very hot cli- 
_Mates this increase of temperature, in front of the storm, will be 
very sensibly felt. 
‘The increased pressure in the annulus round a voleano, when 
it suddenly bursts out, will sometimes under favorable circum- 
stances, be very great, and of course the air will be depressed 
from a great height, so that some portion of the very air which 
has gone up in the central parts of the ascending column, and 
