10 Mr Harvey on the Influence of Magnetism 
lance as near as possible to the south pole of the plate, its de- 
tached rate of -f 8".5 was increased to -f ; and, on de- 
taching the chronometer from the magnet, the rate returned to 
d- 8",B, being only 0".2 less than its former detached rate ; and 
which, considering the powerful influence the time-keeper had 
been subject to, by tlie action of the magnet, was in some de- 
gree remarkable. By afterwards placing the same chronometer 
on the plate, so that the centre of its bottom should coincide 
with the middle of the magnet, and that a radial line proceed- 
ing from the centre of the chronometer through the axis of the 
balance might be at right angles with the axis of the magnet, 
the rate declined from -f 8".3 to — 2".6 ; so that the south pole 
of the magnet produced an increment of -j- 19".0 in the rate, 
and its equator a decrement of 10".9. So also, when the centre 
of the chronometer (D) was placed over the middle of the mag- 
netized plate, and the radial line before alluded to was perpen- 
dicular to the axis of the magnet, the detached rate of -f 2".0 
was increased to -f- 3". 1. On removing the chronometer, this 
rate declined to 0".9 ; but, on applying the machine to the north 
pole of the plate, the last mentioned rate was augmented to 
being the same as that produced when the time-keeper 
was applied to the equator of the plate ; but the actual increment 
in the latter case was 2".2, whereas in the former it was only 
I'M ; a necessary effect of the superior energy of the pole of 
the plate. The great effect of the middle of the plate on the 
rates of the chronometer, will not be regarded as remarkable, 
when it is considered that only a single point of the chronome- 
ter could be applied to the equator of the magnet ; and that 
both the balance and the main spring, were in each case beyond 
the centre of the plate, and consequently under the influence of 
an attractive force, less powerful than that developed by the 
poles of the magnet, but much superior to the effect of the 
actual equator of the plate. 
One thing worthy of observation in these experiments is, the 
immediate influence which the magnet exercised on the chro- 
nometers, and likewise the freedom with which they lost the 
magnetic power, when the attractive influence was less energeti- 
cally developed, either from a change in the position of the in- 
strument, or from its being detached from the magnet altogether. 
