and their Causes, , 25 1 



lative to what can not be the cause of the heat in the land 

 winds. 



It remains now to point out a theory., supported on a 

 firmer basis, which I shall endeavour to do in the follow- 

 ing pages. It is founded on a chemical principle, and will 

 explain, I think, the heat of these winds in a satisfactory 

 manner. 



The principle itself needs no demonstration, as it is ad- 

 mitted as a general law ; viz. that " all bodies, when they 

 become more dense, suffer heat to escape ; or, what is the 

 same, they give out heat." For example, when gases or 

 aeriform substances become vapours, they discharge as 

 much heat as was necessary to keep them in their former 

 gaseous state : further, vapours in condensing into fluids 

 are known to do the same, as also fluids, acquiring solidity. 



I am sorry that the quantity of heat set free in the con- 

 v densation of vapours required for a pound of water has 

 escaped my memory; but I recollect it was very considera- 

 ble. We know, however, that a great deal of it is re- 

 quired for the evaporation of the same measure, and it is 

 but reasonable to admit that the same quantity with which 

 it has combined should be discharged oa its returning to 

 its former state of fluidity. 



In order to apply this principle to explain the presence 

 of heat in our land winds, I must first observe, that the 

 atmosphere in January, February, and March, is perfectly 

 clear and serene; and then I will call to mind what has 

 been said of the phenomena of those winds, that they are 

 preceded by clouds on and among the Ghauts, and that a 

 heavy shower of rain from that quarter announces their ar- 

 rival ; that during their continuance clouds are observed to 

 lie on the Ghauts ; and that the atmosphere, even in the 

 low country, is hazy and thick. I must add also, that the 

 countries west of the Ghauts are at this season frequently 

 visited bv heavy showers of rain, accompanied with much 

 thunder and lightning, and sometimes with hail. Here in 

 the Mysore country I have found the heaviest showers of 

 this kind to come from the north-west*, which is exactly 

 in the direction of the countries remarkable for the great 

 heat of the land winds in this season. At times, wc have 

 also showers from the east and south-east, and my attention 

 shall not be wanting to ascertain whether it is not at the 

 time when the land winds blow hottest in the Carnati-j. 



* The hottest land winds in this season ( 1 S04) at Madras were, I uader- 

 stand, from the north-west ; which corresponds with the direction trom which 

 the rains came in Mysore at that period. 



By 



