﻿144 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



of Great Britain, among mountains, the average yearly rainfall is 

 from 45 to 150 inches, and in the west, away from the hills, from 30 to 

 45 inches, while in the eastern counties it is only from 20 to 28 inches. 

 This very large effect is produced by mountains of moderate extent and 

 of average elevation of 2,000 to 3,000 feet. At Bergen, in Norway, 

 the fall is 89 inches ; at Goimbra, in the Spanish Peninsula, 118 inches; 

 at Xantes, 51 inches, and at Bayonne 49 inches. In parts of Sweden 

 and Eussia it is as low as 15 inches; in France the average is 30 inches; 

 in the plains of Germany and Russia 20 inches. 



But the most striking instance of the rain-compelling power of moun- 

 tains is afforded by the Khasia Hills, situated about 200 miles north of 

 the head of the Bay of Beugal, and only about one-third of the height 

 of the Himalayas. Here the annual rainfall is said to be 600 inches, of 

 which 500 fall in seven months. At 20 miles farther inland, beyond the 

 hills, the annual amount is reduced to 200 inches; at 30 miles to 100 

 inches; and at Gowahatty, in Assam, to 80 inches. In the more west- 

 erly Himalayas, where the southwest monsoon has already been drained 

 of part of its vapor by passing over a tract of dry land and hilly coun- 

 try, the rainfall is only 120 to 140 inches. Similar instances occur in 

 India, e. g., Bombay, on low ground, 75 inches; among the Western 

 Ghauts, at Uttra Mullay, 263 inches; at Poouah, more inland, 24 inches. 



In Mauritius, at Oluny, in the vicinity of mountains and exposed to 

 the southeast trade wind blowing from the sea, the rainfall in almost 

 any month is from four to six times greater than at Gros Cailloux, on 

 the northwest coast, only 16 miles distant. 



In England the difference between hilly and level districts is well 

 observed in the winter, when the clouds are low, and when precipita- 

 tion is less due to ascensional currents than to vapor-laden winds. The 

 clouds on rainy days in winter are very frequently between 500 and 

 1,000 feet above the sea level. The effect of low hills is consequently 

 most marked at this season. Dartmoor, Exmoor, the Chiltern, Cots- 

 wold, Derbyshire, Surrey, and Hampshire hills severally raise the 

 observable rainfall above that of the surrounding country. At the 

 head of the valley of Longdendale, near Manchester, nearly 1,000 feet 

 above the sea level, the rainfall in 1859 was 53^ inches; on the west 

 side, and just over the summit on the east side, 58 J inches. At Peni- 

 stone, a few miles farther east, it was 39 inches, and at Sheffield, still 

 farther east, 25 inches. The height of the hills producing this effect is 

 about 1,400 feet. Similarly, the fall varied from 39.1 inches at Eoch- 

 dale to 67 inches at Blackstone Edge (1,200 feet), 32.25 at the east- 

 erly foot of the ridge, and 20 inches at York in 1848. In 1859 a gauge 

 on the westerly side of Loch Ard gave 92 inches, while another near 

 Glenfinlas, farther east, gave only 48 inches. The instances of Slieve 

 League, of Hoy, and of the South Downs show that it is not only moun- 

 tainous masses, but also mere barriers against the wind from the rainy 

 qaurter which cause precipitation. The air will be equally lifted to 



