THE ENGLISH LAKE DISTRICT. 109 



at Seathwaite, and, in the Winter months of those years, 03 per cent, and 3-4 

 per cent, respectively less rain fell on the mountains than in the valley. But, in 

 1852, 3 per cent, less rain fell in the Summer and 1-5 per cent, more in the Winter 

 months, than descended in the subjacent valley ; and, in 1853, the fall is less than 

 in the valley, both in the Summer and the Winter months. In the years 1850 

 and 1851, the relative excess of rain on the Stye, 948 feet above the Sea, was 27-6 

 and 21-5 per cent., but in 1852 and 1853, only 81 and 97 per cent, respectively; 

 hence, in the memorably wet year 1852, this station received nearly 2 inches 

 less rain than in 1851, and 21 inches less than in 1850. 



The above tables shew that on the mountains, the greatest depth of rain in- 

 variably obtains at Sparkling Tarn, 1900 feet above the sea level. The current 

 which brings our principal supply of rain is the South-west. It is characterized by 

 a high temperature — is generally at or near the point of saturation — and, in most 

 heavy and continuous rains, the depth of the stratum of vapour is considerable, 

 extending from a thousand feet or less above the sea to probably 4000 or 5000 feet 

 above it. In passing over the comparatively level tract of country between the 

 coast and the mountain ranges, rain is deposited, but with little diminution in 

 the temperature of the gases or vapour. The current is at length arrested in its 

 progress by the hills — the vapour in contact with the bases of the mountains is 

 subjected to more rapid condensation, during which it gives out a portion of its 

 latent heat in a sensible form, whereby the temperature of the surrounding mass 

 of air and vapour is increased, and, by virtue of its increased elasticity, it rises to 

 a greater height ; the diminution of temperature due to the increased elevation 

 causes fresh deposition — the surrounding medium is again warmed — the vapour 

 ascends still higher — is farther cooled, and more water forced from it ; and thus, 

 the same operation is continued and repeated, so long as an adequate supply of 

 vapour is furnished from beneath. Hence, in the upper regions of the atmosphere, 

 there is a vertical as well as a lateral current of vapour constantly rushing in to 

 supply the loss by precipitation. 



In ascending from the valley, the amount of vapour which the atmosphere is 

 capable of supporting or containing in mechanical combination is found to diminish, 

 while the difference between the air and dew point temperatures also gradually 

 decreases. There must therefore be a point of elevation, where the quantity of 

 vapour and the degree of humidity will combine to produce a maximum deposit 

 of rain in a given time ; and this plane of greatest condensation is found, in the 

 English Lake District, at or about 2000 feet above the sea-level. 



It does not follow, from what has just been stated, that the same law would 

 hold good in the open atmosphere, (supposing it were possible to plant a gauge 

 therein at an altitude of 2000 feet) because the rate of cooling upwards is much 

 more sudden in ascending on the surface, than obtains in rising abruptly from the 

 surface, as in a balloon ; consequently, the temperature at any given elevation on 



VOL. XXI. PART I. 2 G 



