﻿] 46 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



In Scotland the rainfall of the northern part of Elgin and !N"airn, 

 protected by the mountains intervening between it and the west coast, 

 is less than half that of western Sutherland, Inverness-shire, and Skye. 

 Portree, in Skye, has 81.75 against 25.87 at Inverness. The east coast 

 of Scotland, generally, is very much drier than the west, although the 

 large precipitation during east winds tends to counteract the effect 

 which the mountains westward have in reducing its rainfall during 

 the prevalence of the equatorial currents. Great differences in rainfall 

 may exist within a small area; for instance, the rainfall at Perth is 

 only 32.10 and at Ochtertyre 44.17 against 50 at Lochearnhead, and 

 the rainfall at Bothwell Oastle is only 29.98 against 115.46 at Ardlui. 

 At Braemar, at the height of 1,114 feet, the rainfall is only 36.50, 

 owing to the great mass of high mountains toward the south and west. 



In Ireland the greatest amounts are registered on the southwest and 

 west coasts, and the fall diminishes inland eastward of the mountains, 

 until in the northeast corner the average is only about 30 inches 

 against 60 to 80 in the west. 



Among the above instances the most instructive, perhaps, for the 

 present purpose are the records of Midhurst, Petworth, and Arundel, 

 compared with those a little south and north of these stations. It is 

 plain that the action of the long, wall like ridge of the South Downs, 

 not exceeding 600 feet in average height, is sufficient to cause from 5 

 to 10 inches excess of rain in its immediate neighborhood, the rainfall 

 20 miles westward and 8 miles southward, being only about live sixths 

 of that which occurs in close proximity to this ridge. Part of the defi-( 

 ciency on the coast must be attributed to the frequent exemption from 

 heavy showers which form over the land, but not over the sea, in sum- 

 mer. The present author has observed this, especially on days with a 

 light westerly or southerly breeze, and has also noted the preference 

 of thunderstorms for the low ground between the hills and the downs. 

 The greatest fall takes place at Midhurst, which lies about 5 miles 

 north of the South Downs, and at the foot of the southern slope of a 

 second ridge, Henley Hill, about 600 feet high, which stretches from 

 east to west. Compared with Dunsfold, about 17 miles to the north- 

 east, the amount is in the proportion of 4 to 3. Dunsfold is probably 

 deprived of a good deal of rain by the mass of Blackdown (900 feet) 8 

 miles to the south. Fernhurst, near a cleft or dale in some high hills 

 on its northern side and 2 miles north of Henley Hill, has, roughly, 

 7J inches less than Midhurst. That even lower hills (400 feet) in a 

 flat country may raise the rainfall of their climate by 5 or 6 inches is 

 shown by the records of the high ground of IS^orfolk and Lincolnshire. 



Now, the practical inference from these statistics is that it may be 

 possible where desirable to imitate natural barriers on a small scale 

 and to increase rainfall in their proximity in order to diminish it else- 

 where. Thus, if between Chichester and Arundel the natural height 

 of the Downs were to be raised by 300 feet, the rainfall would be 



