RAINS AND RFV^ES. 113 



rivers never go diy and our springs fail not ? It is becanse of 

 tliese air-crossings — these beautiful operations, and the exquisite 

 compensation of this grand machine, the atmosphere. It is exqui- 

 sitely and wonderfully counterpoised. Late in the autumn of the 

 north, throughout its vanter, and in early spring, the sun is pour- 

 ing his rays with the greatest intensity doAMi upon the seas of the 

 southern hemisphere, and this powerful engine which we are con- 

 templating is pumping up the water there (§ 268) with the greatest 

 activity, and sending it over here for our rivers. The heat which 

 this heavy evaporation absorbs becomes latent, and, wath the mois- 

 tm-e, is carried through the upper regions of the atmosphere until 

 it reaches om- climates. Here the vapour is formed into clouds, 

 condensed, and precipitated. The heat which held this water in 

 the state of vapom' is set free, it becomes sensible heat, and it is 

 that [(4), § 288] which contributes so much to temper our winter 

 chmate. It clouds up in ^\inter, turns warm, and we say we are 

 going to have falling weather. That is because the process of con- 

 densation has abeady commenced, though no rain or snow may 

 have fallen : thus we feel this southern heat, that has been 

 collected fi'om 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 om' northern winter. If Plate I. fairly 

 represent the coui'se of the wands, the south-east trade-^ands would 

 enter the northern hemisphere, and, as an upper current, bear into 

 it aU then- moisture, except that which is precipitated m the region 

 of equatorial calms, and in the crossing of high momitain ranges, 

 such as the Cordilleras of South America. 



291. The South Seas, then (§ 290), should supply mainly the 

 Jiore rain in the watcr for this eugiuc, whilc the northern hemisphere 

 thrjmhernVcmi- coudenscs it ; we should, therefore, have more rain in 

 ^P^^""®- the northern hemisphere. The rivers teU us that 



we have — the rain-gauge also. The yearly average of rain in the 

 north temperate zone is, according to Jolmston, thirty-seven inches.. 

 He gives but twenty-six in the south temperate. The observations 

 of mariners are also corroborative of the same. Log-books, contain- 

 ing altogether the records for upwards of 260,000 days in the 

 Atlantic Ocean north and south (Plate XIII.), have been care- 

 fully examined for the pm-pose of ascertaining, for comparison, the 

 number of calms, rains, and gales therein recorded for each hemi- 

 sphere. Proportionally the number of each as given is decidedly 

 greater for the north than it is for the south. The resdt of this 



