70 MR BROUN ON THE BALANCE MAGNETOMETER, 
commencing with a large arc, than if it belong to a series commencing with a 
small one. 
These conclusions I had arrived at nearly two years ago, and accordingly 
only small arcs were used in determining the time of vibration, seldom above 5’.0 
commencing. 
The following series of observations was made in January 1844, before re- 
moving the needle for the purpose of determining its temperature correction. 
Many other series made previously give the same result; but the following will 
be sufficient to prove the facts stated above. 
TABLE II. 
Observations for the Time of Vibration of the Balance Needle in the Vertical 
Plane, for different Arcs. 






Semi-are of Vibration. Means. 
Time at the Number 
commencement off 7 > +) =i) pee een f. of 
pack: Barley: Beginning. Ending. enone. Partial. Of the Series. 
d bh WwW id ‘4 
Jan. 26 22 15 1.8 0.4 14 9.58 
22°25 1.4 0.4 14 9.58 
22 40 25.0 18.6 6 VAS H 
18.6 6.5 6 10.98 10.95 } 
6.5 0.5 8 10.71 
22 53 1.3 0.4 16 9.78 
23 20 1.6 0.4 16 9.70 
23 32 45.5 25.0 6 11.36 
25.0 11.3 8 11.20 
11.3 6.5 6 11.07 11.07 
6.5 Bit 6 10.95 
21 0.5 6 10.78 
23 50 irg 0.4 14 10.17 
Jan. 27 0 5 55.0 40.0 6 11.72 
40.0 30.0 6 11.60 
30.0 22.0 6 11.57 
22.0 17.0 6 11.45 
17.0 12.3 6 11.37 11.35 
12.3 5.8 6 11.33 
5.8 5D, 6 11:22 
5.5 4.5 6 11.09 
4.5 0.7 6 10.80 
0 20 ky 0.4 18 10.60 


The semi-arcs were observed by my assistant Mr Wetsu, at one microscope, 
while the times of each vibration were observed by myself at the other. 
It is not my intention, in the present communication, to enter into any 
examination of the causes of these peculiarities; my object is simply to pomt 
them out as sources of error. I shall therefore merely state my conclusions, with 
their evidences. 
6. 4th, The time of vibration in a vertical plane depends, to a considerable 
extent, on the temperature of the needle. 
