MR. DAN I ELL ON A NEW REGISTER-PYIIOMETER 
*268 
The following’ Table collects these results into one view, and exhibits the 
expansion denoted by each reading, and the mean result. 
Table III. 
0 
1 
17 
= 
.01119 
1 
23 
= 
.01206 
1 
16 
= 
.01105 
1 
23 
— 
.01206 
1 
20 
= 
.01163 
1 
23 
= 
.01206 
Mean 1 
20 
= 
.01163 
The temperature of the atmosphere was about 64° during these observations. 
Exp. *2. A bar of soft iron, of the same dimensions as that of platinum, was 
substituted for the latter in the register. The experiment was repeated five 
times : twice with the register immersed in the mercury, and three times 
exposed only to the vapour. The time of exposure varied from twenty minutes 
to ten, from the first moment when the metal began to boil. 
The following Table exhibits the several readings and the appropriate 
expansions. 
Table IV. 
2 13 = .01933 
2 33 = .02224 
2 10 = .01890 
2 23 = .02079 
2 20 = .02036 
Mean 2 20 = .02036 
The greatest variation from the mean was therefore only j^dths of an inch in 
the platinum experiment, and j^dths in the iron. 
We shall now compare these results with the preceding determinations of 
MM. Dulong and Petit. 
