1847.] 



Bottom Heat. 



337 



* Mean of two years only. 



t Result of 1843 only. 



Upon this Professor Forbes observes, that the following conclu- 

 sions are plainly deducible: 



1. The temperature of the ground at Trevandrum, is from 5° to 

 6° Fahr. higher than that of the air. This result is confirmed 

 by observations on the temperature of springs and wells at Tre- 

 vandrurn, which have been obligingly communicated to me by 

 Major General Cullen, of the Madras Artillery. These observa- 

 tions are printed in the proceedings of this .society. 



2. When the monthly means of the thermometers are projected 

 so as to show the curves of annual temperature, they are found to 

 have one great inflection and a smaller one. The principal max- 

 imum of the temperature of the air occurs about the beginning of 

 April, after which the rainy season sets in, and the annual curve 

 goes through its extreme rajige in three months; the principal 

 minimum occurring about the middle of July. The femaining: 

 fluctuations are comparatively insignificant, but indicate a slight 

 maximum about the middle of October. 



3. The epochs of temperature are retarded with the depth be- 

 low the surface in the usual manner, and, at the same time, casual 

 fluctuations disappear, and the ranges diminish. At 12 French 

 feet, the principal maximum occurs five V\^eeks later than in the 

 open air, and the range is still at least a degree and a half. 



From these facts it is easy to infer that the phenomena of the 

 propagation of heat into the ground near the equator resemble 

 those of temperate latitudes, though modified in extent and cha- 



