AQUEOUS ATMOSPHERIC PHENOMENA. 



473 



4. In countries beyond the tropics, where the periodicity of rain disappears, and it falls 

 at any hour of the day, or on any day of the year, the quantity is not uniformly dis 

 tributed through the different months, but the largest amount usually descends in some 

 particular season. Thus, at Lisbon, the quantity is insignificant in summer, and at its 

 maximum in winter ; while in the interior of Germany, it is just the reverse. Europe may 

 be divided into three great regions of seasonal predominant rains. 



Province of the winter rains, , 

 Province of the autumn rains, 

 Province of the summer rains, 



South of Portugal, Spain, and Italy, with Greece. 

 ( Remainder of Southern Europe, with the West and North coast of 

 I France, Great Britain, the Netherlands, and Norway. 



Interior Europe, with Denmark, Sweden, and Russia. 



5. The amount of precipitation decreases generally in proportion as countries are 

 removed from the ocean, because the land supplies a less quantity of vapour than the sea. 

 Thus it declines from a fall of between 30 and 35 inches on the shores of Great Britain 

 and France, to less than half that quantity in the interior of Russia. But mountain- 

 chains occasion several exceptions to this rule. 



6. More rain falls on mountainous districts than on low and level regions, for their 

 lofty heights arrest the course of the clouds, and promote the condensation of vapour by 

 their cold summits. Proceeding from Paris to the Alps, the following differences occur : 



Paris, ... .... 20 inches. 



Valley of the Middle Rhine, . . . . 21 



Berne, at the foot of the Alps, . . . . 43 n 



Great St Bernard, highest meteorological station in Europe, . 63 * 



Highlands and predominant winds sometimes occasion an excess of rain in a country on 

 one side of the chain, while a vast reduction occurs on the other. This is strikingly 

 exemplified in the instance of Norway and Sweden, divided by the Scandinavian Alps. 

 At Bergen, on the Norwegian coast, there fall annually 82 inches, or more than at any 

 other city in Europe, and more than the amount at many places within the tropics. The 

 clouds brought from the Atlantic by the prevailing south-west winds, are arrested by the 

 mountains and confined in the fiords, where they accumulate, and lose their moisture, as 

 it were, by mechanical compression, so that the sea-winds discharge nearly all the water 

 held in suspension in passing the chain. Hence it frequently rains for entire days in 

 Norway, while only a few drops fall in Sweden, on the opposite side of the range ; and 

 the mean annual fall in the latter country is only 20 inches. 



7. The highlands which line the west coast of Great Britain, along with the prevailing 

 south-west winds, sweeping from an enormous expanse of the ocean, render the annual 

 amount of rain greater on the western side of the island than in the central and eastern 

 districts. This appears from the table : 



