124 or rain. 



Rain oamoun- 6. That the quantities of rain collected at the (op of high 



Iw thra. P,ain ' mountains ' and on P lains about half a mi,e diftant from tho,e 

 mountains are nearly equal, but in fummer there falls fome- 

 what more on the plains, and in winter fomewhat lefs. Phil. 

 Tranf. 1771, p. 295. The greater quantity of rain collected 

 in fummer on plains appears to me to proceed from the caufe 

 juft mentioned, the lefs difturbed flate of the atmofphere; but 

 the quantity of rain gained through the influence of this caufe 

 is often, in great meafure, compenfated by that arifing from 

 the condenfation of fogs formed on the fummits of mountains, 

 particularly at night, when neither fog nor rain exift on the 

 plians. But in winter, thefe mifts being much more frequent 

 and denfer on the fummits of mountains, the quantity of moif- 

 ture which they depofit is tar more confiderable. 

 More rain on the 7. That it rains much more on the weftern coafts of moil 

 wefterly coafts p ar t s of Europe, particularly if mountainous, than in the in- 

 terior parts of thofe countries, or on the eaftern coafts of the 

 Britannic iflands. 



The caufe of thefe phenomena is very obvious. Wefterly 

 winds are by far the moft frequent in moft parts of Europe ; 

 thefe flow from the Atlantic which bounds it, and generally 

 convey marine clouds electrified differently from the foil or 

 land over which they flow, as alfo from that of the higher 

 clouds under which they reign. Hence proceeds their mu- 

 tual attraction, and thence rain. This effect muft take place 

 principally on the weftern coafts ; when they proceed further, 

 this different electrical ftate muft either ceafeor be diminithed. 

 When the coafts are mountainous, thefe mountains quickly ab- 

 ford the ele£tric matter contained in the weftern blafts, and by 

 collifion, condenfe the vapours they contain, firft into clouds, 

 and finally into rain. Hence it often happens that wefterly 

 winds, particularly in fummer, produce no rain, either be- 

 caufe they introduce no clouds, or meet with none differently 

 electrified. 

 Countries where 8 * That in fome countries it fcarce ever rains. — This arifes 

 it never rains, from local circumftances, as is apparent in the following in- 

 Peru. fiances : 1. It never rains on the plains of Peru from the gulf 



of Guyaquil, nearly under the equator, up to latitude 23° 

 fouth, nor is thunder ever heard there, though thefe plains 

 border on the Pacific Ocean, but they receive a flight dew 

 every night. Bouguer, fig. de la Terre XXIII. 2 Ulloa*s 



Mem. 



