1855.] Report on the Kooloo iron Mines. 199 



feet beneath the level of the sea. This depth must be still greater, 

 but the mean temperature of the village of Munnikurn not 

 being known, I was obliged to take for a starting point 63° 

 Eaht. which is certainly too high. This reminds me how import- 

 ant it would be, to determine, in the different parts of India, 

 the line of invariable temperature of the earth ; we should then 

 have the mean temperature of places without being obliged to 

 perform long and tedious thermometric experiments, which cannot 

 always be performed with exactitude every where, and we should 

 equally be able to obtain more accurate notions of the nature of 

 the climate and vegetation. I am well aware that the mean tem- 

 perature of such localities as have been inhabited for a length of 

 time by Europeans is well known, but it is seldom that those loca- 

 lities offer the scientific interest met with in isolated places, in 

 mountainous countries for example, which are only occasionally 

 visited, and in which, for that reason, a long series of thermome- 

 trical observations can rarely be taken. 



It results from observations made in Europe and America, that 

 the invariable line of temperature increases in depth, as we approach 

 the poles, and that it diminishes as we increase the distance from 

 them. In the temperate climate of Europe, it varies between 79 

 and 89 feet beneath the surface of the earth, whilst under the 

 tropics the larger invariable is found at 13 inches. These data 

 lead us to conclude, that in India we should not have to excavate 

 to any great depth to find the larger invariable, showing the mean 

 temperature. 



The thermal springs of Munnikurn, though they belong to the 

 class of the warmest met with in nature, do not however reach the 

 highest degree of temperature known. In fact, the heat of 202° is 

 exceeded by many other springs, and to give two examples, I will 

 name those of Camarguillas in Mexico indicating 205.5, and those 

 of Las Teruncheras, the temperature of which has increased within 

 the last 24 to 25 years from 194.5 to 206.6, Eaht. Two facts 

 characterise the thermal springs of high temperature ; 1st, their 

 purity, that is to say, the minimum portions of mineral substances 

 which they contain ; 2nd, the variability of their temperature. I 

 am not aware, if the waters of Munnikurn have or have not under- 



2 D 



