104 THE PHYSICAL GEOGRAPHY OF THE SEA. 



rain wrung out of these winds for these American rivers by the 

 Andes, that they become dry and rainless after passing this bar- 

 rier, and as such reach the western shores of the continent, pro- 

 ducing there, as in Peru, a rainless region. The place in the sea 

 whence our riv'ers come, and whence Europe is supplied with 

 rains, is clearly not to be found in this part of the ocean. 



278. Between the parallels of 80° and 35° N. lies the calm belt 

 The calm belt of Can- of Cauccr, a Tcgiou whcrc thcrc is no prevaiU7-ig 

 no rain. wiud (scc Diagram of the Winds, Plate I.). It is a 

 belt of light airs and calms — of airs so baf&ing that they are often 

 insufficient to carry off the "loom," or that stratum of air which, 

 being charged with vapor, covers calm seas as with a film, and as 

 if to prevent farther evaporation. This band of the ocean can 

 scarcely be said to furnish any vapor to the land, for a rainless 

 country, both in Africa, and Asia, and America, lies within it. 



279. All Europe is on the north side of this calm belt. Let us 

 The North Atlantic ©xtcnd our scarch, then, to that part of the Atlantic 

 S^n^for^rJIe^^a ^hich Hcs bctwcen the parallels of 85° and 60° K, 

 Sron? sfxlif (rfaii to SCO if wc havc water surface enough there to sup- 

 theiand. p|y pains for the 8-| millions of square miles that 

 are embraced by the water-sheds under consideration. The area 

 of this part of the Atlantic is not quite 5 millions of square miles, 

 and it does not include more than one thirtieth of the entire sea 

 surface of our planet, while the water-sheds under consideration 

 contain one sixth part of its entire land surface. The natural pro- 

 portion of land and water surface is nearly as 1 to 3. According 

 to this ratio, the extent of sea surface required to give rain for 

 these Si millions of square miles would be a little over 25, instead 

 of a little less than 5 millions of square miles. 



280. The state of our knowledge concerning the actual amount 

 Daily rate of evap- ^^ cvaporatiou that is daily going on at sea has, not- 

 th5n°on^iand— 'oS withstanding the activity in the fields of physical 

 nervations wanted, j-gsearch, bccn but little improvcd. Eecords as to 

 the amount of water daily evaporated from a plate or dish on 

 shore afford us no means of»judging as to what is going on even 

 in the same latitude at sea. Sea- water is salt, and does not throw 

 off its vapor as freely as fresh-water. Moreover, the wind that 

 blows over the evaporating dish on shore is often dry and fresh. 

 I: comes from tlie mountains, or over the plains where it found 



