VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 279 



only be admitted as giving a true result, for it was found on cooling the spirit 

 down from 100° to 30°, that the contraction from 6o° to 30° had been increased 

 by 1 ; so much of the fluid being left behind in the upper p;irt of the 2 tubes, 

 as appears on its being heated up again to 6o°, for then it stood lower in the 2 

 tubes by 1 than it did before; care having been taken that the upper part of the 

 2 tubes should be as dry as possible before the experiment commenced, for which 

 purpose the instrument was charged over night, and constantly kept in a vertical 

 position. It must also be obvious that 397, which was found for the total ex- 

 pansion in heating up from 30° to 100°, must likewise be too great by nearly the 

 same quantity, it having been cooled down from 6o° to 30° previous to its being 

 heated up to 100°, as this would tend to make it sink so much lower than it 

 would have done in the first instance had that not been the case. 



After the above experiments, the spirit was poured out, and, previous to the 

 repetition of the foregoing experiments on a future day, it was charged with 

 more of the same spirit which was used in the former experiments, and the in- 

 strument was hung up as before. Having brought it to the temperature of 60°, 

 the spirit in the 2 tubes was found to stand at 4 above 0. I cooled it down to 

 30°, when it stood in the 2 tubes at l6o.5 below O. I brought it again to the 

 temperature of 6o°, and it was found to stand in the 2 tubes at 4 above O as 

 before. It was then heated up to 100°, and was found to stand in the 2 tubes at 

 236 above O. I cooled it down again to 30°, and found it to stand in the 2 

 tubes at l62 below O. It was then brought again to the temperature of 6o°, 

 and was found to stand in the 2 tubes at no more than 2.5 above 0. 



From the precedina^experiments it appears, that the contraction in cooling 

 down from 6o° to 30°, is l60.5 +4= l64.5, and in heating up from 30° to 

 6o° again, the expansion was the same. In heating up from 60° to 100°, the 

 expansion was 236 — 4 ^ 232, therefore the total expansion in heating up from 

 30° to 100° will be 396.5 ; but in cooling down again from 100° to 30°, we shall 

 have for the total expansion 236 + 162 = 398. The former quantity of 396.5 

 differs 1.05 in defect, and the latter 0.45 of a division in excess, from the expe- 

 riments by weight: but it is obvious from this, as well as from the preceding 

 experiment, that the method of heating up from 30° to 100° can only give the 

 true expansion, as has already been observed; for when the spirit is cooled down 

 from 60° to 30° the expansion will be made greater than it ought to be; as it 

 was found on setting off, that the spirit in the 2 tubes at 6o° of temperature 

 stood at 4 above 0; and after having been cooled down to 30°, and heated up 

 again to 6o°, it was found to stand the same; but after having been heated up to 

 100°, and cooled down again to 30°, the contraction from do" to 30° was found 

 greater by 1.5 than before; and on heating up to 6o° again, it was found to stand 

 only 2.5, instead of 4, above 0. It is therefore very reasonable to conclude. 



