OF THE VIBRATIONS OF AN INVARIABLE PENDULUM. 
229 
Whence it appears that at the same height of the barometer, 30.193 inches, 
the pendulum made 8.515 vibrations per diem more in hydrogen gas than in 
atmospheric air ; the temperature of the gas being 39°.32, and of the air 38°. 1. 
The hydrogen gas was obtained under Mr. Newman’s superintendence, by 
the action of zinc upon dilute sulphuric acid; and was collected in a gasometer 
previous to its transfer into the apparatus, which was effected through the 
metallic pipe usually connected with the air-pump. The cylinder containing 
muriate of lime was made a part of the communication between the apparatus 
and the gasometer. 
Exp. VIII. — February 10th, 11th, and 12th. Clock gaining 4 m 14 s .38. 
The hydrogen having been again pumped out till the gauge showed 0.7 
inch, a fresh atmosphere of hydrogen was introduced by Mr. Newman with 
every possible care to ensure its purity ; when the following observations 
were made. 
Observer. 
=■1 
Thermometers. 
Included 
Times of 
Arc registered and 
true Arc. 
Correc- 
Reduct. 
to 36°. 
Corrected 
o.S 
"z. o 
CJ 
1 
4 
Barom. 
Disapp. 
Re-app. 
Coincidence. 
Interval. 
tion for 
Arc. 
Vibrations 
at 36 
r 
1 
o 
O 
inch. 
m s 
15 58 
m s 
16 15 
2 
3 
39.8 
39.7 
29.84 
24 23 
32 48 
24 39 
33 05 
> 11 24 31.33 
0.765 = 0.92 
80 
23 25 
25 17 
33 54 
- 
S 
s 
s 
Mr. 
81 
32 04 
>507-705 
+ 0.35 
+ 1.58 
86314.95 
Taylok.^ 
82 
40 42 
42 21 
8.3 
84 
39.7 
39.7 
29.82 
49 07 
57 44 
06 20 
50 40 
59 04 
>22 49 55.43 
0.107 = 0.128 
J 
85 
07 34 
15 53 
86 
14 51 
1 
39.75 
29.83 ; 
Index + 0.32; 
Reduction to 32° — 0.03; = 
30.12. 
86314.95 
A bottle was then carefully filled with the hydrogen gas from the apparatus 
by Mr. Newman, and conveyed by him to Mr. Faraday at the Royal 
Institution for examination, from whom I have since received the following 
note. “ I have examined the hydrogen gas, and find no appreciable quantity 
of air in it. If it contains any, it is less than a o odtli part ; and this I think will 
be as nothing in your experiments.” 
The remainder of the hydrogen was then pumped out of the apparatus to 
