316 Recent Fossil Fresh-water deposit, fyc. [No. 148. 



that the spring under description is fast drying up, for the Reddy of 

 the village pointed out to me land, now waste, which, within the last 

 forty years, had been irrigated by it. It now yields but a scant supply 

 to the cattle and the beasts of the forest. The traditionary accounts of 

 diminishing temperature are by no means so satisfactory, since the 

 Hindoos had no means of measuring warmth or cold. 



However, the examination of the deposits in and around the mouth 

 of this spring goes to support what the natives say, assuming that 

 the more siliceous deposit containing the fossils is of an older date 

 than the two at the bottom of the spring, and formed when the spring 

 was more abundant, and its water hot enough to hold a considerable 

 quantity of silica as well as lime in solution, possibly combined. As the 

 heat decreased, the water would lose most of its silica, but still retain 

 the lime ; at this period it may be inferred, that the kunker was preci- 

 pitated as the water cooled on the earth's surface. As the heat still 

 diminished, the portion of lime brought up in solution decreased to the 

 state in which we now see it. That such is the fact appears from 

 the circumstance of the water of two other and warmer springs, which 

 I have since discovered in the same formation, holding considerably 

 more lime in solution than this. 



The waters of two other thermal springs in the same formation still 

 deposit lime as a kunkrous incrustation on their sides and on the rocks 



in their course. 



These had a higher temperature ; viz. 90° and 91° 3' ; the minerals 



held in solution are similar, but the proportion of lime is greater. One 



fact is worthy of note, that they were all slightly alkaline, and contain- 



ed no perceptible free carbonic acid. 



In order to ascertain the interesting problem, as indicated by the tra- 

 ditions of natives, and the difference between the quantity and quality 

 of the present and ancient deposits; viz. that the heat of this part of 

 the interior of the globe is decreasing, it would be desirable to keep a 

 register not only of the thermal springs of S. India, but of those far 

 hotter fountains that gush from the great Southern line of dislocation of 

 the Himalayan strata, and the trap hills of Central and Western India. 

 The heat of the springs might be annually or triennially noted 

 with compared thermometers. After many experiments, I find ex- 

 isting meteorological causes generally affect the temperature of such 

 springs in a sensible degree; and great care should be taken, in 



