1838.] On the spontaneous heating of Brine* 1015 



the probe in 1838 ; although the reservoir in question was filled under 

 very similar circumstances both years, and with brine of nearly full 

 saturation to the depth of eight feet, the superstratum of eight feet (in 

 all sixteen feet) being however, when first filled up, much nearer satura- 

 tion in 1837 than in 1838. But to this difference I attach less im- 

 portance than to the more rapid extraction of the strong brine from 

 below in June, July, and August, 1838, than in the corresponding 

 months of 1837, when a large proportion of the strong brine remained 

 in the reservoir till the end of the year. It is nevertheless remarkable 

 that the maximum temperature in this reservoir, which so far exceeded 

 that of any other in 1837, was in 1838 even less than the maximum at 

 the bottom of a small reservoir (No. 2) at Bally a Ghat, containing 

 only a small portion of strong brine not exceeding two-thirds saturation. 

 Altogether twelve deposits of brine at the several salt works have 

 been subjected to trial, and, contrary to what might have been expected, 

 the greatest heat (121°) has been found in the smallest mass ; namely, 

 in a small pool of bittern and salt drainings with superincumbent rain 

 water in a hole dug for a well at Ballya Ghat : and this high tempera- 

 ture continued, rather increasing than otherwise, from the beginning of 

 November to the middle of January, when the water was taken out. In 

 all these deposits the brine remained the whole time undisturbed, 

 except in No. 2 of the Ballya Ghat series, (till after the 22nd June,) and 

 Nos. 4 and 5 of the Narainpore series, whence it was pumped out to 

 supply the salt-boilers, the two latter from June to the 23rd September 

 inclusive, and afterwards No. 5 during all November, and No. 4 from 

 the beginning of December. In every one of them some heating may be 

 discovered ; for I now think the temperatures of 91° and 92 9 in the lower 

 strata of No. 3 of the Bhaota series may be regarded as at least 2° or 

 3° higher than would have been found in an equal mass of fresh water 

 at the same date. But it would seem that the heating scarcely begins 

 to shew itself till the saltness of the water exceeds that of the ocean 

 (S. G. 1028). It would also appear that the heating is most rapid 

 where the greatest differences exist in the saltness of contiguous strata 

 of water ; and that it is both accelerated and more quickly terminated 

 by agitation. This will easily be perceived on comparing No. 2 of the 

 Narainpore series with No. 1 and 2 of Bhaota, and Nos. I and 4 of 

 Ballya Ghat ; the very large diameter and smaller depth of the first 

 causing the contents of that reservoir to be more affected by the wind 

 than those of the other places named. Nevertheless, even in that large 

 reservoir the lower strata, as far as four feet from the bottom, appear 

 6 M 



