24 BappickER—On the Influence of Magnetism on the Rate of a Chronometer. 
Scoresby concludes: ‘The regularity of a change of rate, from losing to gain- 
ing, with each reversion of position in the watch, everything else being the same, 
was a sufficient proof that some part of the watch was magnetic and that that part 
was acted upon by the influence of the magnet.” 
Scoresby’s general considerations about the influence of terrestrial or artificial 
magnetism on an unmagnetic balance deserve some attention. For it does not 
appear to be so obvious, that a magnet should not have any influence upon an 
unmagnetic balance. This would be the case if the balance was a steel disc, for 
instance; but as the cross-bar will always exceed the other steel so considerably in 
quantity, it is very probable that a magnet would tend to alter the are of vibration, 
and thus to affect the rate of the chronometer, especially when the cross-bar at rest 
was in a line with the magnet. How far this influence goes remains to be deter- 
mined experimentally ; it is probably very small, as it is certainly in the case of 
terrestrial magnetism, but it may become perceptible to careful observations. 
These observations would have to determine how strong a magnet must be in order ~ 
to produce a sensible effect upon the rate of a chronometer, the steel parts of which 
have been proved to be free of magnetism. That an inversion of poles would—in 
such a case—not have any effect is obvious; and so Scoresby’s experiment certainly 
proves some magnetic quality in the watch. Where it lies, however, is not to 
be ascertamed. Hardly anything else can be deduced from his experiment, as 
it seems to be in every respect a rough and preliminary one only. 
The means of counteracting the earth’s magnetic influence on a watch will be 
discussed further on (cf. p. 45). 
WALT. 
[Grorcre Harvey. ] 
The leading idea in all the experiments as yet mentioned was, that the balance 
and perhaps its spring were the chief bearers of any magnetic quality, and the chief 
medium through which external magnetic action affected the chronometer’s rate. 
George Harvey (Nos. 10-13) is induced to make his experiments by the assump- 
tion that a change of rate takes place chiefly with changes in the position of the 
‘‘main-spring” relative to the direction of the magnetic force. Notwithstanding 
this, he considers the balance to be the part of the chronometer chiefly acted upon 
by the magnet, as is seen from his attempt to explain the different effects of the 
same force upon different instruments. Leaving every discussion as to the correct- 
ness of this supposition till later on, I will proceed to describe his experiments, 
which possess some new, and for further experiments not quite worthless, features. 
Harvey experimented at first with a bar magnet, 131 inches long, 14 inches 
broad, and + of an inch thick, which was of considerable power, and one pocket 
