2 
Mr Harvey on the Influence of Magnetism 
to the direction of the magnetic force ; and hence the situation 
of the spring, with relation to the attracting pole, was particu- 
larly attended to. The magnet was of the bar form, 13 J inches 
long, 1| inches wide, a quarter of an inch thick, and possessing 
considerable power. 
For this purpose, the magnet was placed in a horizontal posi- 
tion, in the direction of the magnetic meridian, with its north 
pole towards the northern horizon. A pocket-chronometer (A), 
possessing a very steady and uniform rate of -|- 20" (the mean 
of seventeen days’ observation, and during which time the great- 
est deviation from the mean amounted only to three quarters of a 
second), was placed in the position denoted by Fig. 1. of Plate I., 
with the centre of its main-spring in the direction of the axis of 
the magnet, and the spring itself as nearly in contact with the north 
pole as the case of the chronometer would permit. The conse- 
quence of this application was, an immediate increase in the rate 
of the machine, from -}- 20" A to -p 65.'T, and which it continued 
to maintain during the four days in which the chronometer occu- 
pied this position. By turning it, however, a quadrant, so as to 
bring the radial line passing through the centre of the spring 
into a position at right angles with the axis of. the magnet, as in 
Fig. 2.y the rate underwent a remarkable declension, from 
to — 2S".2; being an alteration in its rate amounting 
to 88".3 ; ^nd when the machine was afterwards brought into 
the position of Fig. 3., so that the centre of its main-spring 
might be again in a line with the prolonged axis of the magnet, 
the alteration was scarcely less remarkable; an increase having 
become immediately perceptible from — 2%" .2 to -p 43".4 ; and 
when the chronometer was subsequently changed to the position 
of Fig. 4., with the radial line before alluded to at right angles to 
the magnetic axis, a losing rate was again perceptible, the change 
being from -P 43".4 to — 2".0 ; and, on restoring the machine to 
the position it occupied in Fig. 1., the rate became -p a 
quantity greater by T^6, than its former rate in the same situa^ 
tion ; — affording another proof of the great accelerating in- 
fluence of the magnet, when the attractive power was transmitted 
through the centre of the main-spring of the chronometer. The 
difference between ‘the results obtained in the two applications 
of the chronometer, in the position denoted by Fig. 1., will not 
