1849.] 



exercised by Trees on Climaie. 



455 



It will be observed from tbe map, that Puttnapoorum the 1st sta- 

 tion from Quilon, at 25 miles from the sea, is just where the high 

 road enters the mass of high mountain ridges and spurs running out 

 from the great chain of ghats. 



From hence to the pass through the ghats, an interval of about 20 

 miles, is a dense mass of chains and groups of high mountain ridges 

 from two to four and five thousand feet in altitude, running parallel 

 to each other in a north-westerly direction, and covered with primeval 

 forests. The gradual increase in the fall of rain up to Caldoorty at the 

 very base of the ghats is very remarkable, as well as its sudden de- 

 crease on the east of the ghats at Shencottah, an interval of only 12 

 miles, causing a diminution from 128 to 46 inches. 



There are no forests of consequence at Puttnapooram, nor for se- 

 veral miles farther to the eastward, and the fall of rain therefore 

 should have diminished rather than increased as we proceeded inland; 

 but, as I have already noticed, the groups and chains of mountains 

 co-mmence at that place, and they become more numerous and higher 

 as we approach the main line of ghats. 



The increase therefore, in the fall of rain at Puttnapooram, and 

 from thence to Caldoorty, I should be disposed to ascribe almost ex- 

 clusively, to the obstruction offered to the passage of the vapour over 

 these high chains of mountains, and to its consequent condensation, 

 and in no way to any effect of the forests. 



Very remarkable examples of this effect of continuous chains of 

 high land, in arresting and condensing the passage of the vapour 

 have been recently afforded in the tables of the fall of rain on the 

 Mahabaleshwar hills, at Mercara in Ooorgh, and on the table land 

 called Uttree Mullay, in the chain of ghats east of Trevandrum, and 

 published in the proceedings of the British Association for the ad- 

 vancement of science — all of these places being from four to nearly 

 five thousand feet above the sea. 



Uttree Mullay is a continuous mass of high land, running for 

 several miles nearly parallel to the coast, in the latitude of Trevan- 

 drum, and upwards of 4,500 feet above the sea. While the fall of 

 rain at Trevandrum is only from 50 to 60 inches, — on Uttree Mullay 

 it is not less than, from 240 to 280 inches. 



The slopes of the mountains are clothed with forests of tall trees, 

 but on the summit, although with much wood, the trees are compara- 

 tively dwarf and stunted. 



