154 Things not generally Known. 



Now when, from continued evaporation, the air is highly 

 saturated with vapour, though it be invisible and the sky cloud- 

 less, if its temperature is suddenly reduced by cold currents de- 

 scending from above or rushing from a higher to a lower lati- 

 tude, its capacity to retain moisture is diminished, clouds are 

 formed, and the result is rain. Air condenses as it cools, and, 

 like a sponge filled with water and compressed, pours out the 

 water which its diminished capacity cannot hold. What but 

 Omniscience could have devised such an admirable arrange- 

 ment for watering the earth ? 



INORDINATE RAINY CLIMATE. 



The climate of the Khasia mountains, which lie north-east 

 from Calcutta, and are separated by the valley of the Burram- 

 pooter River from the Himalaya range, is remarkable lor the 

 inordinate fall of rain the greatest, it is said, which lias ever 

 been recorded. Mr. Yule, an English gentleman, established that 

 in the single month of August 1841 there fell 264 inches of rain, 

 or 22 feet, of which 12^ feet fell in the space of five consecu- 

 tive days. This astonishing fact is confirmed by two other 

 English travellers, who measured 30 inches of rain in twenty- 

 four hours, and during seven months above 500 inches. This 

 great rain-fall is attributed to the abruptness of tiie moun- 

 tains which face the Bay of Bengal, and the intervening flat 

 swamps 200 miles in extent. The district of the excessive rain 

 is extrem ly limited; and but a few degrees farther west, rain 

 is said to be almost unknown, and the winter falls of snow to 

 seldom exceed two inches. 



HOW DOES THE NORTH WIND DRIVE AWAY RAIN ? 



We may liken it to a wet sponge, and the decrease of tem- 

 perature to the hand that squeezes that sponge. Finally, reach- 

 ing the cold latitudes, all the moisture that a dew-point of 

 zero, and even far below, can extract, is wrung from it ; and 

 this air then commences " to return according to his circuits" 

 as dry atmosphere. And here we can quote Scripture again : 

 " The north wind driveth away rain." This is a meteorolo- 

 gical fact of hig.i authority and great importance in the study 

 of the circulation of the atmosphere. Mauri/. 



SIZE OF RAIN-DROPS. 



The Drops of Rain vary in their size, perhaps from the 25th 

 to the of an inch in diameter. In parting from the clouds, 

 they precipitate their descent till the increasing resistance op- 

 posed by the air becomes equal to their weight, when they 

 continue to fall with uniform velocity. This velocity is, there 



