122 Ma HARVEY on a Remarkable Case of Magnetic Intensity 



passed through an arc of 90 ; when a deviation of the south 

 pole immediately followed. 



When the Chronometer was so placed that the transverse 

 arm, which bears the time-screws of the balance, became east and 

 west, a fine compass-needle, having its centre over the middle of 

 the balance, immediately disposed itself in the same direction, 

 its north pole reposing over the screw which possessed southern 

 polarity. When also the balance was turned through an arc of 

 90, the needle turned with it, the north pole in consequence 

 pointing to the south. The moment, however, the balance was 

 allowed to vibrate, the needle commenced its oscillations, vibra- 

 ting in progressively decreasing arcs, from the first semicircle de- 

 scribed by it, to zero in the magnetic meridian, where it main- 

 tained a small tremulous motion. In another experiment, when 

 the balance was turned through a greater arc than a quadrant, 

 before motion was communicated to the Chronometer, the needle 

 was nearly inverted, the north pole pointing west ; and on mo- 

 tion being given to the balance, the needle ranged for many se- 

 conds through the complete circumference, until the directive 

 power of the earth, by gaining the ascendancy, caused the arcs 

 of vibration successively to diminish, the needle ultimately ob- 





