Intertropical Springs and Fivers. 107 



tiness of rain,- — the favourable conditions of the atmosphere for irra- 

 diation, — and the capacity of the soil for imbibing and giving out 

 the solar heat. The temperature of the granitic soil in the vicinity 

 of Bellary, at 2 p.m., in May, reached 121°; that of the Regur, or 

 black soil, 122°-5 : the temperature of the air in the shade, 95°-5; 

 at midnight, the temperature of the black soil was still so high as 

 86°; temperature of the air 80°. That of a bare rock of granite, 

 the same locality, at 2 p.m., was 120°-6 ; of black basaltic rock, 152°. 

 The temperature of the granite at midnight was 86°*5. Both Bel- 

 lary and Hydrabad are situated under the shade almost of bare gra- 

 nitic masses, in the midst of plains covered with sheets of the granitic 

 and black Regur soils just alluded to, whose almost treeless extent, 

 during the hot months, is shrunk up and intersected by deep and 

 countless fissures. The climato of the former station is nearly as 

 dry as that of Egypt. In 1838, only 11-25 inches of rain fell dur- 

 ing the year. The atmosphere is remarkable for transparency and 

 freedom from clouds. The foregoing views appear to be strengthened 

 by the fact, that the observed mean temperature of the elevated sta- 

 tions of Otacamund (7221 feet above the sea's level), Mercara (4500 

 feet), and Candy, in Ceylon (1680 feet), are lower than their calcu- 

 lated mean temperatures. Thecalculatedmeanof Otacamundis61°*64, 

 observed mean 55°-8 ; of Mercara 68°-99, observed mean 65°*58; and 

 of Candy 78°'58, observed mean 73°*3. Now, all these places are sur- 

 rounded by an irregular surface hill and valley, generally clothed with 

 eternal frost, presenting an extensive radiating and evaporating sur- 

 face, and shading the drainage of heavy monsoons that lingers in their 

 swampy hollows. The humidity of the atmosphere at these stations 

 is very great ; at Mercara, during nearly half the year, its hygrome- 

 tric condition closely approaches saturation. Hence, favoured by the 

 alternations of land and sea breezes, even close to the sea level, the 

 low temperature of some places near the equator, viz. : — Singapore, 

 lat. 1° 15' N., mean temperature 80°-7 ; Malacca, lat. 2°'14N., 

 mean temperature 80°*4 ; Penang, lat. 5° N., mean temperature 

 80°'5 ; Province Wellesley, lat. 5° 20' N., mean temperature 79°5. 

 The monsoons are distributed over these forest-clad regions of the 

 equator in an almost daily succession of refreshing showers through- 

 out the year. May not the vital functions of the plants, covering 

 large tracts of country, particularly those concerned in their respira- 

 tion and nutrition, exert an influence in cooling over-heated states 

 of the atmosphere ? 



It may be farther stated, in corroboration of the high tempera- 

 ture of tablelands being mainly produced by the causes referred to 

 above, that the temperature of isolated peaks and summits of ridges, 

 rising with a rapid ascent and confined superficies from their ele- 

 vated level, appears to diminish in a great/^r ratio than 1° Fahr. 

 for every 352 feet of ascent ; when, perhaps, that of the aggregate 



