1856.] Our Climatic Vicissitudes. 297 



•with warm and moist air, then the rain will be violent; but if slowly 

 cooled, the rain will distil gently. Should it le cooled but little below 

 the point of saturation, then only clouds or fog will appear. 



It is evident, from these considerations, that whatever moisture the 

 western current may acquire in its passage over the Pacific, would be 

 nearly all relinquished by the time it arrived at the cold tops of the 

 Eocky Mountains ; and as it plunges down into the warm regions of the 

 Mississippi Valley, it would greedily drink of all water in its way. 



This, then, accounts for the notable dryness of the American climate, 

 as compared with that of England. There the western current flows 

 over the warm waters of the Gulf Stream, becomes charged with moist- 

 ure, and, as it strikes the chalky cliffs of Albion, gives out both warmth 

 and moisture. 



But some to whom this subject is new may inquire, " why it is, if the 

 western winds are dry, that all our violent storms come from that direc- 

 tion ? " By carefully noting the principles just given, the reason will be 

 obvious. Previous to the storm, the air is close and warm ; you look at 

 the thermometer, and it indicates, we will say, 86 degrees, and full of 

 moisture; for when you pour out a glass of cold water to quench your 

 thirst, you notice that its outside is instantly bedewed ; the air contains, 

 then, if fully saturated, ^^ of its weight of water. The least exertion 

 produces copious perspiration ; for the full air refuses the exhalations. 

 The birds cease singing — all is mute. 



" We often fee against some storm 

 A silence in the heavens : the rack stands still, 

 The bold winds speechless, and the orb below 

 As hush as death : anon the dreadful thunder 

 Doth rend the region.'' — Hamlet. 



Then comes the dashing rain and wind ; then the cloud passes, the 

 sun breaks through, while the cool west wind blows and drives every 

 cloud from the sky. Now look again at the thermometer ; it has fallen, 

 say, to 59 degrees. If so, then a quantity of watfcj equal in weight to 

 g-y the weight of the air or thereabouts, has been precipitated to the 

 earth as rain. No other storm will occur until the western wind ceases 

 to blow. 



Such is the history of the great majority of our violent storms. Now, 

 what has caused the rain? Evidently the sudden intrusion of the cool 

 western current upon the warm moist air, which had come to us frum th» 

 Gulf of Mexico. 



Sometimes the south-east wind, which also comes to us from warmer 

 regions, is gradually cooled by its northern journey, and its moisture 



