VOL. LXVI.] PHILOSOPHICAL TRANSACTIONS. 35 



XI y. Experiments on IFater obtained from the Melted Ice of Sea-lVater, to 

 ascertain ivhether it be fresh or not ; and to determine its Specific Gravity with 

 resbect to other Water. Also Experiments tojind the Degree of Cold in which 

 Sea Water begins to freeze. By Mr. Ediv. Nairne. p, 249. 

 The sea water used in the following experiments was furnished by Mr. Owenj 

 of the Mineral Water Warehouse, at Temple Bar ; who assured Mr. N. that it 

 was taken up off the North Foreland. On Jan. 27, 1766, at 10 in the evening, 

 Mr. N. filled a jar, 3^ inches in diameter and 6i inches deep, with seawater, 

 and exposed it to the open air, the thermometer standing at 13°. At noon the 

 next day, on taking it in, he found it frozen very hard, except a very little at the 

 bottom, which remained quite fluid. The ice, when taken in from the open air, 

 was 4- of an inch above the edge of the jar. He now set it by a stove in a heat 

 of 5d° to thaw. When the jar had continued in this degree of heat for 8 hours, 

 he took out the ice, which was then 3-i- inches long and 2 inches in diameter ; 

 about \ of the water appeared to remain. In order to clear the ice from any 

 brine that might adhere to it, he washed it in a pail of pump water, in which it 

 was suffered to remain about a quarter of an hour, and then set it in a sieve to 

 drain off the water in which it had been washed. On Jan. 29, he set the 

 beforementioned ice in a basin in a heat of about 46°, in which it continued 9 

 hours before the whole was dissolved. The bulb of a thermometer rested on the 

 ice during the time of the solution, and continued without variation at 32°. 

 The water thus obtained was, to his palate, perfectly free from any taste of 

 salt. 



To ascertain the comparative gravity of this water, Mr. N. filled a bottle with 

 it to a certain mark in its neck, which was very narrow, and weighed the bottle 

 so filled very carefully. He weighed the same bottle, filled to the same mark in 

 its neck with seawater, and other waters successively, which were all brought to 

 the same degree of heat by a thermometer. The results were as follow; 

 videlicet. 



Grains. 



Water obtained from the melted ice of the seawater l6l4 



Distilled rainwater 1012 



Water taken out of a water tub, being a mixture of rain and snow water 161 5 



The seawater l653 



The residuum of the seawater from which the ice beforementioned had been taken. . 1659 



To find the degree of cold in which seawater begins to freeze, Mr. N. made 

 the following experiments. He exposed to the open air a decanter filled with the 

 seawater, in which a thermometer was suspended, the bulb of which reached to 

 the middle of the widest part of the decanter ; a jelly-glass filled with the same 

 seawater, in which also a thermometer was put, resting on the bottom, was 

 placed in the same exposure. The result will be seen in the following table : 



F 2 



