1844.] Recent Fossil Fresh- water deposit, §c. 315 



parted with most of their colour ; and some are quite empty as if imbed- 

 ded but yesterday ; most have been evidently entombed in a dead state. 



As no trap or other volcanic rock was at hand to account for the 

 silicification of this fresh- water limestone, I proceeded to examine the 

 present deposit of the spring a few yards West of the fossil bed. Its 

 water I discovered to be slightly thermal, having a temperature of 

 85° 3' Farht. which is a few degrees above the mean temperature of the 

 spot, isothermally calculated ; the height above the sea as roughly ap- 

 proximated by the boiling point of water, is about 1250 feet, and the 

 average temperature of the ordinary wells about 80° Farht. 



The present deposit of these waters is a brownish-grey calcareous 

 mud, about six inches thick, mingled with sand, imbedding similar fresh- 

 water shells and a minute specimen of paludina. Stems of grasses and 

 leaves were also found in it ; some of the latter apparently just decay- 

 ed, while others are blackened by carbonization ; none were fossilized. 



Below the mud lay a deposit of nodular kunker, quite distinct 

 in character from that of the fossil bed, being white and earthy, externally 

 pulverulent or chalky, but internally compact and hard. I did not 

 observe any shells or plants in it. The depth of this layer could not 

 be ascertained for want of leisure, and better instruments for digging 

 under water than a geological hammer. 



The water of the spring is tasteless, inodorous, and free from gaseous 

 bubbles ; and, instead of any free carbonic acid gas, is slightly alka- 

 line, turning reddened litmus paper into a faint greenish blue ; oxalate 

 of ammonia, and muriate of baryta produced a considerable white 

 precipitate. That from the muriate of baryta effervesced with dilute 

 nitric acid, shewing the precipitate to be carbonate of lime. A thin 

 slice of gall nut suspended in the water, detected a trace of iron. A 

 minute portion of silica remained after evaporation. 



The present layer of mud then, as we have just seen, is more of a 

 mechanical deposit than the subjacent white kunker, which is evidently 

 a chemical precipitate, and concretionary in character, while that which 

 has fossilized the shells and plants, is far more siliceous : so much so in- 

 deed, as to resemble in some parts the siliceous tufa deposited by the hot 

 springs of Iceland, more than the common calcareous kunker of India. 



The natives declare, that both the volume and heat of these thermal 

 springs, (of which I have within the last two years discovered several in 

 the diamond formation,) are on the decrease. There is no question 



