REPRESENTING THE VELOCITY OF SOUND, 
211 
moment, and in which the interval of time between the flash and the report 
was correctly observed at both extremities of the base. 
Date. 
No. of the 
Observa- 
tion. 
Barometrical Pres- 
sure reduced to 0° 
Centigr. and cor- 
rected for capillarity. 
Metres p. 
Tension of 
Aqueous Vapour 
in Metres T. 
Temperature, 
Centigrade 
Thermometer. 
t. 
Time elapsed 
between Flash 
and Report. 
1823. 
June 27 
1 
0.74450 
0.0095347 
12.08 
seconds. 
52.035 
3 
0.74455 
0.0095474 
12.08 
51.790 
4 
0.74455 
0.0094585 
12.01 
51.695 
5 
0.74465 
0.0096998 
11.94 
51.860 
6 
0.74455 
0.0095347 
11.88 
51.850 
8 
0.74470 
0.0094459 
11.67 
51.950 
9 
0.74470 
0.0093697 
11.60 
51.845 
12 
0.74475 
0.0093697 
11.25 
51.865 
13 
0.74470 
0.0092173 
11.25 
51.945 
17 
0.74500 
0.0093697 
10.47 
51.960 
18 
0.74505 
0.0092173 
10.40 
52.055 
19 
0.74495 
0.0092173 
10.40 
52.025 
23 
0.74480 
0.0089888 
10.28 
51.995 
24 
0.74470 
0.0088364 
10.14 
51.945 
25 
0.74475 
0.0088364 
10.07 
52.020 
26 
0.74480 
0.0084683 
10.00 
51.335 
June 28 
4 
0.74830 
0.0084638 
11.89 
52.020 
5 
0.74775 
0.0083921 
11.09 
51.525 
6 
0.74800 
0.0084638 
11.53 
52.245 
7 
0.74820 
0.0081763 
11.25 
32.315 
8 
0.74815 
0.0081763 
10.78 
52.215 
9 
0.74815 
0.0083159 
10.42 
52.675 
10 
0.74835 
0.0083921 
10.28 
51.175 
14 
0.74810 
0.0081763 
10.14 
52.445 
15 
0.74810 
0.0082524 
10.42 
51.965 
17 
0.74815 
0.0086206 
10.97 
51.875 
18 
0.74805 
0.0086968 
10.89 
52.240 
19 
0.74805 
0.0087730 
11.12 
52.080 
Length of base, 17669 metres. 
From this Table and the following data, the results obtained by M. Dulong 
were compared with Drs. Moll and Van Beek’s experiments. 
The weight of a cube centimetre of mercury at the temperature of 0° Centi- 
grade, is 13.596152 grammes. This is according to the experiments of MM. 
Biot and Arago, and MM. Dulong and Petit’s subsequent investigations. 
The weight of a cube centimetre of dry atmospheric air, at zero of Centigrade 
scale, and under the barometric pressure of 0 m .760 is, according to the same 
observers, 0.001299541 grammes*. 
* Biot, Traite de Physiq. Exper. et Matliem. t. i. p. 402, seqq. and p. 3S7. 
2 E 2 
