362 THE PHYSICAL GEOGEAPHY OF THE SEA. 



now and tlien, and on rare occasions, that ships carry rain-gauges 

 to sea. We can determine by quantitive measurements the dif- 

 ference in amount of precipitation on the land of the two hemi- 

 spheres ; and it is the result of this determination, I imagine, that 

 has given rise to the general remark that the rain-fall is greater 

 for the northern than it is for the southern hemisphere. But we 

 have few hyetographic measurements for quantity at sea ; there the 

 determinations are mostly numerical. Our observers report the 

 "times" of precipitation, which, whether it be in the form of rain, 

 hail, or snow, is called by the charts, and in this discussion, rain. 

 Among such a large corps of observers, rain is sometimes, no doubt, 

 omitted in the log ; so that in all probability the charts do not 

 show as many " times" with rain as there are " times" actually with 

 rain at sea. This omission, however, is as likely to occur in one 

 hemisphere as in the other. Still, we may safely assume that it 

 rains oftener in all parts of the sea than our observations or the 

 rain charts that are founded on them indicate. 



1013. "With the view of comparing the rains at sea between the 

 parallels of 55° and 60°, both in the North and South Atlantic, 

 we have taken from the charts the following figures : 



South — Observations, 8410 ; gales, 1228 ; rains, 1105 



;^orth— " 526; " 135; " 61 



Gales to the 1000 observations . . S. 116 ; N. 256 



Eains " " ..S. 131; N. 121 



That is, for every 10 gales, there are in the southern hemisj)here 



9 rains, and in the northern 4.7. In which hemisphere does most 



water fall on the average during a rain at sea ? Observations do 



not tell, but there seems to be a philosophical reason why it should 



rain not only oftener but more copiously at sea, especially in the 



extra-tropical regions, in the southern hemisphere, than in those 



of the northern. On the polar side of 40° IST., for example, the 



land is stretched out in continental masses, upon the thirsty bosom 



of which, when the air drops down its load of moisture, only a 



portion of it can be taken up again ; the rest is absorbed by the 



earth to feed the springs. On the polar side of 40° S. we have 



a water instead of a land surface, and as fast as precipitation takes 



place there, the ocean replenishes the air with moisture again. It 



may consequently be assumed that a high dew point, at least one 



as high as the ocean can maintain in contact with winds blowing 



