VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 275 



but the 2 methods in this experiments differ very considerably from each other, 

 namely, by no less a quantity than ^ divisions. In this experiment it seems pro- 

 bable either that some of the spirit leaked out at the stopper, or that the stopper 

 shifted its place a little, so as to enlarge the capacity of the ball. 



The contraction by the short instrument in cooling down from 6o° to 30° was 

 l66 — 2 = 164, and the expansion on heating up again to 6o°, the same. On 

 heating up to 100°, it was 230 + 2 = 232, but on cooling down again to 6o° 

 the contraction was 230 + 5 = 235; the mean is 233.5, and the total expan- 

 sion 397.5; differing from the experiments by weight 0.05 of a division, in de- 

 fect. The difference between the 2 methods, in heating up from 6o° to 100°, 

 and in cooling down again from 100° to 6o°, is 3 divisions. 



It appears from the preceding experiments, that the mean of all the quantities 

 found on heating up from 30° to 100°, and cooling down from 100° to 30°, taken 

 together, gives for the total expansion 397. 1 6 by the long instrument, and 396.5 

 by the short ; the former errs O.39, and the latter 1 .05 divisions from the expe- 

 riments by weight, in defect. It appears also that the mean of all the quantities 

 found by the long instrument, on heating up from 30° to 100°, gives for the 

 total expansion 4.34 divisions less than the mean of all the quantities taken toge- 

 ther, by the same instrument, on cooling down from 100° to 30°; and the dif- 

 ference by the short instrument is 2 divisions. 



The following experiments were made with a mixture of equal parts of spirit 

 and water by weight; the spirit being of the strength already mentioned. 



Having charged the instruments with the mixture, and brought it to the tem- 

 perature of 6o°, it was found to stand in both of them at 1 above O. The mix- 

 ture was then cooled down to 30°, when it stood at 125 below O in the long in- 

 strument, and 124.5 in the short one. It was brought back to the temperature 

 of 6o°, when, in the long instrument it was found to stand J. 5 above O, but in 

 the short instrument 1 above as before. I heated the mixture to 100°, when 

 it stood at 185 in the long instrument, and in the short one at 183.5 above O. 

 The mixture was afterwards cooled to the temperature of 6o°, when it was found 

 to stand 2.5 above O in the long instrument, but in the short one 1.5 below O. 

 After keeping them upright in the temperature of 6o° 2 hours, I found the mix- 

 ture in the long instrument to stand 3 above O, but in the short one 2 below O. 

 I heated it again to 100°, when the mixture in the long instrument was found 

 to stand 1 85, and in the short one 180.5 above O. I brought the mixture again 

 to the temperature of 6o°, and found it stand 2.5 above O in the long instru- 

 ment, and in the short one 4 below 0. 



From the above experiments the contraction of this mixture from 6o° to 30° 

 was found to be, by the long instrument, 125 -f- 1 = 126; but in heating up 

 to 60° again, the expansion was 125 -|- 1.5 = 126.5; the mean is 126.25. The 



N N 2 



