t 108 3 



city with the foregoing. The tumblers were placed on the wall 

 formerly defcribed, and left there covered with glafs until eleven 

 o'clock next morning. 



" In the morning, at eleven o'clock, the Thermometer pointed 

 to twenty-eight. The water in both tumblers was frozen quite 

 through, and formed maffes of ice, tranfparent as cryftal in every, 

 part, except the centre, and near the bottom, which parts were 

 rendered opaque to the thicknefs of half an inch, by a number 

 of air-bubbles locked up in the ice. The diftilled water had 

 been kept feveral days in the jar above defcribed, whofe mouth 

 was only covered with an inverted pewter dim. 



" Into a glafs tumbler, capable of holding a Winchefter pint or 

 more, I put a wine pint of Thames water; and Into another 

 tumbler of the fame figure and capacity, I poured a pint of fea- 

 water concentrated, by freezing one fourth of it, the better to 

 reprefent fea-water of the great oceans, which are not affected by 

 rivers fo much as the fea-water ufed in thefe experiments mult 

 be, as it was taken up near the North Foreland. The fea-water 

 was thus concentrated for thefe further reafons : firft, that the 

 effect of fait in the water might be more confpicuous during 

 the thawing of the ice; and fecondly, to prevent the firft portions 

 of ice thawed from diluting the fait water to a degree, which 

 never is found in the ocean. I reduced the Sea and the Thames 

 water, contained in thefe tumblers, to the fame temperature 

 exactly, in the open air; then taking hold of each by the fum- 

 mit of the glafs above the water, I carried them into my ftudy, 

 and placed them on a carpet fifteen feet equally diftant from the 

 fire, and three inches from the wainfcot of the wall oppofite the 

 fire, and equally diftant from a door on one fide, and a window, 

 which extends within fourteen inches of the floor, on the other. 

 The tumblers, containing the frozen water, were immerfed in 



a large 



