VOL. LXXXIX.] PHILOSOPHICAL TRANSACTIONS. 4g7 



which for some weeks had been regularly heated every day by a German stove, and 

 in which the air was kept up to the temperature of 6l° of Fahrenheit's thermo- 

 meter, with very little variation. Having suffered the bottles, with their contents, 

 to remain in this situation till I conceived they must have acquired the temperature 

 of the circumambient air, I wiped them afresh, with a very clean dry cambric hand- 

 kerchief, and brought them into the most exact equilibrium possible, by attaching 

 a small piece of very fine silver wire to the arm of the balance to which the bottle 

 which was the lightest was suspended. Having suffered the apparatus to remain in 

 this situation about 12 hours longer, and finding no alteration in the relative weights 

 of the bottles, they continuing all this time to be in the most perfect equilibrium, 

 I now removed them into a large uninhabited room, fronting the north, in which 

 the air, which was very quiet, was at the temperature of 29 , p. ; the air without 

 doors being at the same time at 27°; and going out of the room, and locking the 

 door after me, I suffered the bottles to remain 48 hours undisturbed, in this cold 

 situation, attached to the arms of the balance as before. 



At the expiration of that time, I entered the room, using the utmost caution 

 not to disturb the balance, when, to my great surprize, I found that the bottle a 

 very sensibly preponderated. The water which this bottle contained was completely 

 frozen into one solid body of ice ; but the spirit of wine, in the bottle b, showed 

 no signs of freezing. I now very cautiously restored the equilibrium, by adding 

 small pieces of the very fine wire of which gold lace is made, to the arm of the 

 balance to which the bottle b was suspended, when I found that the bottle a had 

 augmented its weight by 3 , ^ o4 part of its whole weight at the beginning of the 

 experiment; the weight of the bottle with its contents having been 48 J 1.23 grains 

 Troy, (the bottle weighing 703.37 grains, and the water 4107.86 grains), and it 

 requiring now T VW parts of a grain, added to the opposite arm of the balance, to 

 counterbalance it. 



Having had occasion just at this time to write to my friend, Sir Charles Blagden, 

 on another subject, I added a postscript to my letter, giving him a short account of 

 this experiment, and telling him how " very contrary to my expectation" the result 

 of it had turned out; but I soon after found that I had been too hasty in my com- 

 munication. Sir Charles, in his answer to my letter, expressed doubts respecting 

 the fact; but, before his letter had reached me, I had learned from my own expe- 

 rience, how very dangerous it is, in philosophical investigations, to draw conclusions 

 from single experiments. 



Having removed the balance, with the 2 bottles attached to it, from the cold 

 into the warm room, which still remained at the temperature of 6*1°, the ice in the 

 bottle a gradually thawed; and, being at length totally reduced to water, and this 

 water having acquired the temperature of the surrounding air, the 2 bottles, after 

 being wiped perfectly clean and dry, were found to weigh as at the beginning of the 

 experiment, before the water was frozen. This experiment being repeated, gave 

 nearly the same result, the water appearing, when frozen, to be heavier than in 



VOL. XVIII. 3 S 



