202 PHYSICS. 
of the barometer on the winds, as shown in pil. 28, figs. 4° and 4%. Now as 
the height of the barometer is in a certain connexion with the temperature, 
the latter must stand in a certain relation to the direction of the wind. In 
Europe, the temperature of the air is generally lower during northern than 
southern winds, and lowest of all during north-east winds ; this rule, 
however, exhibits many occasional exceptions in different places and 
seasons. Thus, in Paris, during summer, it is coldest during south-west, 
west, and north-west winds, and warmest during south-east winds; in 
winter, on the other hand, it is coldest during north, north-east, and north 
winds, and warmest during south, south-west, and west winds. Curves 
exhibiting the connexion between the condition of the thermometer and the 
directions of the wind for a given place, are called by Dove thermometric 
wind rosettes ( figs? 5° and 5?), 
Unusually high winds or storms are caused by some great disturbance of the 
equilibrium of the atmosphere, which, in many cases, is produced by a rapid 
condensation of watery vapor, and the consequent rarefaction of the air; the 
air then rushes violently from all directions to the place of rarefaction, the 
place itself changing its position. This theory is maintained by Brandes 
and Espy. According to Redfield and Dove, storms are to be considered as 
whirlwinds, having a north-eastward progressive motion from the south to 
the north of the tropic of Cancer, the air in the whirl rotating simultaneously 
in a given direction. Inthe northern hemisphere this is from south to north 
by east. In pl. 23, fig.638, AB represents the line along which the minimum 
of atmospheric pressure progresses. The circles described about A and B 
represent the whirl at the beginning and at the end of the storm. At the 
commencement of the storm, south-east or south winds will prevail at places 
south-east of AB; south-east at D and E; south at C and F; at the end of 
the storm the wind will have a westerly direction at these places. To the 
north-west of AB the wind will blow in the opposite direction. In the 
southern hemisphere the whirlwinds move from the north-west, and have the 
opposite direction of rotation. 
Coasts and islands are especially subject to violent storms, owing to the 
absence of the mountains and elevated ranges which so eminently alleviate 
the force of the wind on the main land. On the coast of the North sea, the 
storms occur principally in November, and aré preceded by calms and by an 
uncommonly damp warm atmosphere. Violent storms also occur on the 
coast of Norway, coming principally from the north-west, also ushered in by 
uncommonly warm weather. On the coast of Finmark, thirty-three storms 
were counted in the single year 1798 ; only twenty-six occurred, however, 
at another time during a period of twelve years. In the north frigid zone 
storms from the south-west and south are not rare; the most violent come 
from the south, shifting round to the north. Among the fiercest storms are 
found those which the mistral (north-east wind) produces quite frequently 
on land, on the Mediterranean, and even as far south as Africa. One of 
these, occurring on the 13th of October, 1782, pressed against an opposing 
surface with a force of 12lbs. to the square foot. 
The most terrible storms of all, called tornados, trovados, or hurricanes, 
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