PHILOSOPHICAL TRANSACTIONS. 



37 



VOL. Lxvr.] 



thawed in order to be now exposed again to the open air. The thermometer in 

 the jar continued in the same situation as before. 



Time. 



iTherm. at the 

 Top. 



10 39 

 10 4.2 



10 48 



11 1 



2 I 



11 



11 45 



34.5 



2.9 



28.5 



28 

 27 



27 + 

 26.5 



Therm, at the 

 Bottom. 



35.5 



32 

 30.5 



28 

 24.5 



28.5 

 28.5 



January 30, 1776, A.M. 



Therm, in the 

 open air. 



16.; 



18.5 



19 



Effects, &c. 



The water fluid. 



Ice began to be formed about the glass at the edge of the 

 water. 



Still continued to have ice only about the edge of the water. 



The surface of the water rendered stagnant by the ice. 



The crystals had almost reached the bottom. 



During the half minute employed in this observation, the 

 crystals reached the bottom of the jar ; the lower ther- 

 mometer rose almost instantaneously from '24.5 to 28.5, 

 and was immediately rendered obscure by the ioe. 



The jar was laken in from the open air, and the lower 

 thermometer lifted out of the ice to a sufficient height for 

 the observation. 



From these observations it seems that the freezing point of seawater should 

 be fixed in Fahrenheit's scale at 28.5. As the water, when it began to freeze 

 in 1 experiments, exhibited phenomena different from any Mr. N. had observed 

 before, it may not be improper to subjoin an account of them. At 14'" after 

 8 in the morning of Jan. 31, he put the ja b of the 2d table, containing 

 the same water ; viz. a mixture of rain and snow water, in a window, having 

 the evening before placed a 2d thermometer in it, the bulb of which was just 

 below the surface of the water. This, as well as the thermometer at the bottom, 

 stood at 27.3, and the water was perfectly fluid : the thermometer placed near the 

 jar within the window, was at 23.5. At 27"^ after 8 it began to freeze at the bottom 

 of the jar, the thermometers at the top and bottom standing alike at 27. The in- 

 stant thecrystals began to encompass the ball of the thermometer below, which they 

 very soon did after it began to freeze, the quicksilver rose in it to 32°, the upper 

 one continuing at 27°. Thecrystals continued to shoot upward, and in less than 

 half a minute reached the bulb of the thermometer at the surface, which imme- 

 diately rose to 32°. After 10'" before 6 in the evening of the same day, Mr. N. 

 put the jar a of the 2d table into the open air, its contents the same ; viz. sea 

 water. The thermometers in it were likewise the same, not having been 

 moved; they both stood at 34°; that in the open air at 19.5. At 6 o'clock the 

 thermometer above was at 31°, that below at 28.25. At this lime he discovered 

 some ice on the surface of the water ; but as it was by candle-light, he could 

 not discern its first appearance. At 10"" after 6, the thermometer above was at 

 29°; that below at 26.5. At 1 5"^ after 6, the upper thermometer at 28.5 ; that 

 below at 25°. At 17'" after 6, both the thermometers stood at 28.5, crystals 

 having risen from the bottom covered the ball of that below, on which it rose 

 instantly from 25° to 28.5. The thermometer in the open air continued as at 

 first, viz. at IQ.S. — ^The scale of all the thermometers, used in these experi- 

 ments, was Fahrenheit's. 



