248 



The Winds. 



Table V. — Height of the snow-line above the sea, and 

 mean temperature of summer in the plains, from Humboldt's 

 Central Asia. 



Pla ce. 



Quito 

 Himalayas 



(S. Side) 

 Mt. Ararat 

 The Alps 

 Kamschatka 

 Isle Mageroe 



(N. Cape) 



Mean sum- 

 mer tempe- 

 rature at sea 

 level. 



(Fah.) 

 83-5 



73-4 



78-1 

 65-1 

 54-7 



44-5 



Measured height 



of the snow-line 



above the sea. 



Decrease of 

 temperature. 



The same 

 (from Mr. 

 Glaisher's 

 balloon ex- 

 periments). 



feet 

 15,900 



° (Fah.) 

 51-5 



° (Fah.) 

 45-8 



13,056 



46-4 



40-2 



14,250 

 8,937 



46-1 

 33-1 



42-5 

 31-0 



5,280 



22-7 



21-6 



2,286 



12-5 



11-9 



Difference. 



(Fah.) 

 —5-7 



—6-2 



—3-6 

 —2-1 

 — M 



—0-6 



The regular progression noticed in the last column of dif- 

 ferences, appears to show that the heat of summer on the plains 

 fairly determines the elevation of the snow-line, but the 

 decrement of temperature with the height near the equator 

 appears to be more rapid than that found in the experiments 

 of Mr. Glaisher. 



No better description can be given of the ventilating 

 system of the atmosphere, than that which is contained in 

 Sir John Herschel's work on Meteorology, from whom we 

 borrow the following exposition of the process (Meteoroloqy , 

 p. 54):— 



" In the intertropical seas a steady and copious evaporation 

 is continually going on. The vapour, carrying with it air, is 

 thrown up beyond the levels of equilibrium, where it flows 

 over, and spreads itself out over the upper regions of higher 

 latitudes. Air also, when heated over large tracts, acts by 

 increased elasticity to upheave the superincumbent strata, and 

 by bulging them upwards to destroy their equilibrium, and 

 cause the upper atmosphere to flow over on less heated regions. 

 It is impossible to separate these two dynamical effects. The 

 immediate effect of the application of heat to any region, is 

 to generate an ascensional movement in the incumbent atmo- 

 sphere : a bodily overflowing of its material above, and a relief 

 of barometric pressure below." 



In the Atlantic Ocean, from the equator to 5° N. latitude, 

 the atmospheric pressure is 29 -92 inches. From 30° to 35° N. 

 latitude it is 30*17 inches, and from 25° to 30° S. latitude it is 

 30*11 inches; making the relief of barometric pressure 0*22, or 



