132 CAPT. NEWBOLD ON THE TEMPERATURE OF THE SPRINGS, WELLS 



air 80°. That of a bare rock of granite, the same locality, at 2 p.m., was 120°*5 ; of black 

 basaltic rock 122°. The temperature of the granite at midnight was 86°'5. Both 

 Bellary and Hydrabad are situated under the shade almost of bare granitic 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 in- 

 tersected by deep and countless fissures. The climate of the former station is nearly 

 as dry as that of Egypt. In 1 838 only 1 1*25 inches of rain fell during 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 stations of Ootacamund (7221 feet above the sea's level), Merc^ra 

 (4500 feet), and Candy in Ceylon (1680 feet), are lower than their calculated mean 

 temperatures. The calculated mean of Ootacamund is 61°*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 surrounded by an irregular surface of hill and valley, 

 generally clothed with eternal forest, presenting an extensive radiating and evapo- 

 rating surface, 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 hygromctric condition closely approaches 

 saturation. Hence, favoured by the alternations of land and sea breezes, even close 

 to the sea's level, the low temperatures of some places near the equator, viz. Singa- 

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

 rature 80°*4 ; Penang, lat. 5° N., mean temperature 80°-5 ; Province Wei lesley, 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 

 throughout the year. May not the vital functions of the plants, covering large tracts 

 of country, particularly those concerned in their respiration and nutrition, exert an 

 influence in cooling over-heated states of the atmosphere ? 



It may be further stated, in corroboration of the high temperature of table-lands 

 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 super- 

 ficies from their elevated level, appears to diminish in a greater ratio than 1° Fahr. 

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

 sea's level is in strict accordance with this rule. The mean of a month's observa- 

 tions by Lieut. Campbell, at the summit and base of the rock of Raya-Cottah on 

 the table-land of Mysore, above which it is elevated 500 feet, gave a decrease of tem- 

 perature amounting to 3°-35. The diurnal mean difference between the temperature 

 of the summit of a mountain on the table-land of Bellary, and that of the plain at 

 its base, I found so great as 7°-5 for the 1500 feet of elevation which separates them. 

 This table-land has a mean temperature of nearly 4°-5 above its calculated mean. 

 The difference of temperature of two wells, one at the summit of Mount Sinai, and 

 the other 2000 feet below, amounted to 6°, a result closely approximating that of the 

 comparative observations at Geneva and St. Bernard. 



I 



