AND ITS TEMPERATURE CORRECTION. 69 
TABLE I. 
Observations for the Time of Vibration of the Balance Needle in a Vertical Plane, 
before and after excessive Vibrations. 
Observed Time of one 
: rab. Temperature | Vibration 
Date. CAUSE OF DISTURBANCE. Se one of Needle. | corrected to 
50°. 


| Ee 
1842. Fs ‘ BD 

March 19. 10.14 45.5 10.48 
pee OD. Balance magnet vibrated excessively. 
April 2. 11.02 42.5 11.59 
se 9. 10.94 44.0 11.40 
Oct. 31. ein of “ nee teas 10.05 55.9 9.60 
air of compasses brought inadvertently near 
Nov. 10. { the balance needle. * 
555mg Ge 10.34 51.0 10.26 
em LO. 10.02 50.8 9.96 
1843. 
Sept. 18. 10.60 65.0 9.46 
me OP 10.62 63.7 9.58 
The box of the magnetometer removed, and the 
v1 26, { needle exposed to currents of air. 
SIE 11.20 51.9 11.06 
as BA 10.95 46.1 11.40 
1844. 
April 29 22 9.04 50.2 9.02 
mm ) oO 7 9.50 60.5 8.70 
Box lifted for the purpose of removing an insect, 
wo. 30 7+ and replaced immediately afterwards; vibra- 
tion not excessive. 

a 00 8 10.03 60.5 9:25 
Pe OO 22 8.97 Ov) le S83 
July 22 0 8.23 62.3 7.30 
con PRY 9.10 68.0 1:13 
24 18 Box lifted, and insect removed from beside the 
{ needle. 
25 0 9.80 67.2 8.49 
-. 25 23 9.67 64.5 8.57 
a 26 8 The magnet vibrated by steel. 
- 26 23 10.04 65.4 8.87 
ee 20) 22 9.45 58.5 8.80 
Oct. 30 22 6.97 47.9 7.13 
Nov. 3 22 6.72 43.9 7.18 
3.—78 poe in observatory, who had probably been 
rea a near the magnet with a hammer. 
7 23 7:30 42.5 7.87 
Workmen brought a hammer near the magnet. 
8 21 After the vibration thus produced, the needle 
oa rested in a position differing 1’.6 from its pre- 
vious position.* 
ot 8.24 46.8 8.48 
10 23 8.03 43.7 8.51 
5. 2d, The time of vibration in a vertical plane depends, to a considerable 
extent, on the magnitude of the arc of vibration. 
3d, For the same arc, the time of vibration is greater, if it belong to a series 
« This is the only case in which I determined, at the instant, the effect of excessive vibration on the posi- 
tion of the needle; the effect, though small, is considerable, when compared with the hourly changes; for 
several hours before this vibration, the magnet had not changed its position. 
VOL. XVI. PART I. s 
