246 The Winds. 



THE WINDS. 



BY A. S. HERSCHEL, B.A. 



In a recent pamphlet, by Dr. Klein, on Foretelling the Weather, 

 translated from the Dutch by Dr. Adriani, the atmosphere is de- 

 scribed as being the means of keeping up upon the earth the 

 salutary movement which it constantly requires. The office of 

 the atmosphere by which the various forms of life upon the earth 

 are supported, and conveyed to distant places to renovate its 

 surface, is performed in part by a steady process of distillation, 

 and in part by the perpetual agitation of the winds. The 

 constant round of functions it fulfils will accordingly well 

 repay attention to examine very closely in detail. For present 

 purposes the atmosphere must first be regarded as a vast 

 cryophorus, or as an immense distilling apparatus, having its 

 boiler on the surface of the earth, and its condenser at the 

 summit of the atmosphere. The vertical process of evapora- 

 tion and condensation into rain can then be fitly described, 

 which everywhere takes place in a tranquil atmosphere, in the 

 absence of the horizontal currents of the winds. 



Over the greater part of the equator, and especially on the 

 ocean, where the air is calm, clouds are seen to gather in the 

 morning, which collect before the evening, and break with 

 heavy showers of rain. A fail of two or three inches of rain 

 in as many hours is no uncommon occurrence in those regions; 

 whence the name of " cloud-ring" is applied to these parts 

 of the equator. Wherever under the full heat of the sun the 

 wind subsides, a cloudy season similar to that at the equator 

 commences. In certain places between the tropics, the 

 regular winds are thus suspended when the sun approaches the 

 zenith of the latitude, and a season of "tropical rains/' as they 

 are called, immediately sets in. This happens in April on the 

 Orinoco, in May or June at Sierra Leone and Calcutta ; falling 

 later in the year at each place according to its distance from 

 the line. On the opposite side of the equator the island of 

 Mauritius, situated on the outer border of the trades, is visited 

 in February by heavy rains ; which is also there the hottest 

 season of the year. The rice fields in the valley of the Ticino, 

 in Lombardy, owe their fertility to the tropical rains which fall 

 in summer on its sheltered plains. A part of the European 

 and Asiatic continents, and a part of central America, are 

 described in a less marked degree as districts of "summer 

 rains." This remark is illustrated by the fact, familiar to 

 readers of the Intellectual Observer, that at the mouth of 

 the Danube, in the summer of last year, the rains were noticed 

 to be " quite tropical " in their extent and character. 



