218 DOVE ON THE LAW OF STORMS. 
with precipitous sides. Besides the causes of diminished atmo- — 
spheric pressure in the tropical regions, an additional cause — 
comes into play in the temperate zone, viz. the high tempera- 
ture brought from lower latitudes by the rapid movement of the 
air from that direction. On the 24th of December this was very | 
considerable. In Tolmezzo the thermometer rose to 25° Reau- 
mur in the shade; at Geneva it rose suddenly 5° in the night of 
the 24th and 25th; at 1 a.m. on the 25th it reached 12°5, which 
was its highest point. In Boulogne, Paris, and Hamburg the 
temperature was unusually high. It seems evident that when so 
warm a current of air was flowing towards the Pole over Europe, 
the cold air displaced by it must flow southward in some other 
quarter, and according to the rotation of the whirlwind, this 
might be expected to be in America. In effect, the thermometer 
at Salem in Massachusetts, in the latitude of Rome, stood 
— 10°2 R. on the 24th of December, and a few days later at 
— 14°2 R., and all accounts from America speak of an unusual 
degree of cold. 
But these phenomena are not peculiar to the winter months. 
The storm which ravaged St. Thomas and Porto Rico on the 
2nd of August, was followed in the middle and on the 21st of 
the same month by two very violent storms, which are described 
in detail in Colonel Reid’s work; at the same time unusual 
heat, accompanied by most violent storms of wind and heavy 
rain, prevailed in Kurope. From the 10th to the 20th of August 
the thermometer stood at + 30° R. in Messina, and between 
+ 28° and + 30° at Naples; on the 12th it stood at + 30° at 
Rome, whilst at Rothen and in the Emmethal the torrents, 
swollen by the violent rains, swept along rocks of 60 cwt. In 
Silesia the heat was oppressive. In Gallicia and Prussia this 
unusual heat was followed near the end of the month by remark- 
able cold. This had prevailed in America during the great heats 
in Europe, for at Rochester, in the state of New York, on the 
4th of August, the extraordinary phenomenon of a night frost. 
had been witnessed. 
If in these meteorological phenomena of the temperate zone 
we recognise the manifest influence of the quickly succeeding 
disturbances of the atmosphere within the tropics, we shall at 
once see the reason why deviations from the order of change in 
the direction of the wind, which results from the law of rotation, 
namely, S. W. N. E., are a sure sign of very unsettled weather 3 
