Curiosities of Science. 1 53 



It clouds up in winter, turns warm, and we say we are going 

 to have falling weather : that is because the process of con- 

 densation has already commenced, though no rain or snow may 

 have fallen. Thus we feel this southern heat, that has been col- 

 lected by the rays of the sun by the sea, been bottled away by 

 the winds in the clouds of a southern summer, and set free in 

 the process of condensation in our northern winter. 



Thus the South Seas should supply mainly the water for 

 the engine just described, while the northern hemisphere con- 

 denses it ; we should, therefore, have more rain in the north- 

 ern hemisphere. The rivers tell us that we have, at least on 

 the land ; for the great water-courses of the globe, and half 

 the fresh water in the world, are found on the north side of 

 the equator. This fact is strongly corroborative of this hypo- 

 thesis. To evaporate water enough annually from the ocean 

 to cover the earth, on the average, five feet deep with rain ; to 

 transport it from one zone to another ; and to precipitate it 

 in the right places at suitable times and in the proportions 

 due, is one of the offices of the grand atmospherical machine. 

 This water is evaporated principally from the torrid zone. Sup- 

 posing it all to come thence, we shall have encircling the earth 

 a belt of ocean 3000 miles in breadth, from which this atmo- 

 sphere evaporates a layer of water annually sixteen feet in 

 depth. And to hoist up as high as the clouds, and lower down 

 again, all the water, in a lake sixteen feet deep and 3000 miles 

 broad and 24,000 long, is the yearly business of this invisible 

 machinery. What a powerful engine is the atmosphere ! and 

 how nicely adjusted must be all the cogs and wheels and springs 

 and compensations of this exquisite piece of machinery, that it 

 never wears out nor breaks down, nor fails to do its work at 

 the right time and in the right way ! Mauri/. 



THE PHILOSOPHY OF EAIN. 



To understand the philosophy of this beautiful and often 

 sublime phenomenon, a few facts derived from observation and 

 a long train of experiments must be remembered. 



1. Were the atmosphere every where at all times at a uniform tem- 

 perature, we should never have rain, or hail, or snow. The water ab- 

 sorbed by it in evaporation from the sea and the earth's surface would 

 descend in an imperceptible vapour, or cease to be absorbed by the air 

 when it was once fully saturated. 



2. The absorbing power of the atmosphere, and consequently its 

 capability to retain humidity, is proportionally greater in warm than in 

 cold air. 



3. The air near the surface of the earth is warmer than it is in the 

 region of the clouds. The higher we ascend from the earth, the colder 

 do we find the atmosphere. Hence tho perpetual snow on very high 

 moxintains in the hottest climate. 



