HEAT OX HIGH LAND. 153 



In Upper Peru and Bolivia we find a fruit- 

 ful soil and a numerous agricultural population, 

 at heights fully as great as those of the loftiest 

 peaks of the Bernese Alps. The great lake of 

 Titicaca lies twelve thousand six hundred, and 

 the street pavement of the town of Potosi twelve 

 thousand eight hundred feet above the sea leveL 

 On the north side of the Himalaya, on the high 

 plains of Daba and Doompo (in lat. 31° 15'N.), 

 crops of wheat and barley ripen, even at the height 

 of fourteen thousand feet (Humboldt). 



In determining the isothermal lines we deduct 

 as nearly as possible the lowering of the tempe- 

 rature due to the height at which any place lies. 

 We say, accordingly, that Quito lies on the 

 isotherm of 26° Cent. (78°'8 P.); that Munich, 

 Augsburg, Eatisbon, and other towns of the 

 South-German table-land lie to the south of the 

 isotherm of 10° C. (50° P.), which, as I have 

 mentioned to you before, passes through Karls- 

 ruhe and IVtirzburg towards Bohemia. The 

 mean temperature of the Swiss Alps, reduced to 

 the level of the sea, would amount to 11 0, 2 C. 

 (52°*26P.) 



You will now r understand why, at certain 

 heights above the level of the sea, even in the 

 hottest days of summer, the temperature can never 

 rise above 0° C. (32° P.) ; and why, on moun- 

 tains loftier than this, the snow can never be 

 entirely melted. 



