112 THE PHYSICAL GEOGRAPHY OF THE SEA. 



tiie north, tlirougliout its winter, and in early spring, the sun is 

 pouring his rays with tlie greatest intensity down upon the seas 

 of the southern hemisphere, and this powerful engine which we 

 are contemphxting is pumping up the water there (§ 261) with the 

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

 heat which this heavy evaporation absorbs becomes latent, and, 

 with the moisture, is carried through the upper regions of the at- 

 mosphere until it reaches our climates. Here the vapor is formed 

 into clouds, condensed, and precipitated. The heat which held 

 this water in the state of vapor is set free, it becomes sensible heat, 

 and it is that [ (-i), § 2SS] which contributes so much to temper our 

 winter climate. It clouds up in winter, turns warm, and we say 

 we are going to have falling weather. That is because the proc- 

 ess of condensation has already commenced, though no rain or 

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

 been collected from 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. If 

 Plate I. fairly represent the course of the winds, the southeast 

 trade-winds would enter the northern hemisphere, and, as an up- 

 per current, bear into it all their moisture, except that which is 

 precipitated in the region of equatorial calms, and in the crossing 

 of hish mountain rano-es, as the Cordilleras of South America. 



291. The South Seas, then, according to § 290, should suppl}^ 

 More rain in the li^-'iinly thc Water for this engine, while the north- 

 tii?Shera'hemi° t^^^^i hemisphere condenses it ; we should, therefore, 

 sphere. havc morc rain in the northern hemisphere. The 



rivers tell us that we have — the rain-gauge also. The yearly 

 average of rain in the north temperate zone is, according to John- 

 ston, thirty-seven inches. He gives but twenty-six in the south 

 temperate. The observations of mariners are also corroborative 

 of the same. Losr-books, containins: altosrether the records for 

 upward of 260,000 days in the Atlantic Ocean north and south 

 (Plate XIIL), have been carefully examined for the purpose of 

 ascertaining, for comparison, the number of calms, rains, and gales 

 therein recorded for each hemisphere. Proportionally the num- 

 ber of each is given as decidedly greater for the north than it is 

 for the south. The result of this examination is very instructive, 

 for it shows the status of the atmosphere to be much more unsta- 



