128 PKYSICAL GEOGRArHY OF THE SEA, AND ITS METEOliOLOGY. 



circiilatioh to that part of the coast, thoiigli it bo as heavily 

 cliarged with moisture as at Patagonia, has a greater extent of 

 country over which to deposit its rain, and, consequently, the 

 fall to the square inch will not be as great. In like manner, we 

 should bo enabled to say in what part of the world the most 

 equable climates are to be found. They are to be found in the 

 equatorial calms, where the north-east and south-east trades 

 meet fresh from the ocean, and keep the temperature uniform 

 under a canopy of perpetual clouds. 



300. Amount of evaporation greatest from the Indian Ocean. — 

 The mean annual fall of lain on the entire surface of 

 the earth is estimated at about five feet. 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. All this evapo- 

 ration, however, does not take place from the sea, for the water 

 that falls on the land is re-evaporated from the land again and 

 again. But in the first instance it is evaporated principally 

 from the torrid zone. Supposing it all to be evaporated thence, 

 we shall have, encircling the earth, a belt of ocean three 

 thousand miles in breadth, from w^hich this atmosphere hoists up 

 a la^^er 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 three thousand miles broad, and 

 twenty-four thousand long, is the yearly business of this in- 

 visible 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 j)iece 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 ! The abstract logs at the 

 Observatory in Washington show that the water of the Indian 

 Ocean is warmer than that of any other sea ; therefore it may be 

 inferred that the evaporation from it is also greater. The Korth 

 Indian Ocean contains about 4,500,000 square miles, while its 

 Asiatic water-shed contains an area of 2,500,000. Supposing all 

 the rivers of this water-shed to discharge annually into the sea four 

 times as much water as the Mississippi (§ 274) discharges into the 

 Gulf, we shall have annually on the average an effective evaporation 

 (§ 282) from the North Indian Ocean of G.O inches, or 0.01 65 per day. 



