1838.] On the spontaneous heating of Brine. 207 



V. — On a remarkable heat observed in masses of Brine kept for 

 some time in large reservoirs. By G. A. Prinsep, Esq. 



In the course of my experiments of several years in the manufacture 

 of salt at Balya Ghat, on the salt-water fake east of Calcutta, I have 

 sometimes observed a high degree of temperature at the bottom of the 

 brine reservoirs after they had been filled for some weeks with brine 

 of less than one fourth saturation. But as the greatest heat observed 

 did not exceed 104° Fahr. which was under the maximum heat of the 

 brine on the terraces, whence the reservoirs had been filled, I supposed 

 the high temperature to be merely that of a warm stream of water let in 

 at the hottest part of the day in May or June, and remaining below and 

 unmixed with the cooler surface water, of less specific gravity, after- 

 wards admitted. This opinion was strengthened by the gradual reduc- 

 tion of the temperature below to nearly that of the surface, before the end 

 of the rainy season. I have frequently bathed in one of the reservoirs 

 (about 550 feet long, 35 ft. wide at top and 7 or 8 feet deep), in Sep- 

 tember and October, and have found the temperature of the water then 

 pretty equal throughout. But on plunging into the same reservoir on 

 the 17th September last, I was surprised to find the temperature near 

 the bottom so warm as to be intolerable to the feet. Still however I 

 imagined that the heat was only that which the sun had imparted to the 

 terrace brine in the very sultry weather of June last, when I had 120° 

 registered (4th June, 4 p. m. ) for the brine of a terrace yielding salt: 

 and believing the hottest water to be therefore near the bottom I tried 

 the temperature there about a month afterwards by immersing an empty 

 bottle at the end of a bamboo, fixing the mouth so that it would be filled 

 about a foot from the ground. The contents when poured out were at 

 the temperature of 120°. A similar experiment made on the same day 

 in a circular brine reservoir at Narainpore (120 feet diam. and about 16 

 feet deep) gave 104°. But on a subsequent visit to Narainpore on the 

 29th October, I was startled to observe that a pump fixed against the 

 wall of this reservoir, for the purpose of feeding the boilers, was actu- 

 ally bringing up water of the temperature of 130° from a depth of 

 about 12 feet. This very unexpected discovery determined me to con- 

 trive an instrument that should serve as a probe to ascertain both the 

 temperature and the specific gravity or saltness of the water at different 

 depths. Annexed is a drawing of the instrument employed : it con- 

 sisted of a split bamboo with bamboo buckets fixed between at distances 

 of one foot from centre to centre, the mouths of the buckets being 

 corked but the corks having small air-holes ; and the mode of using the 

 machine was, to let it down with the mouths of the buckets downwards, 

 and then turn it round after which the air bubbles indicated the progress 

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