30 Bappicker—On the Influence of Magnetism on the Rate of a Chronometer. 
of the magnet, the induced and permanent magnetisms of the steel parts, and 
the terrestrial magnetism are in equilibrium, so as to produce no change of rate 
at all: their position depends, therefore, upon the quantity and distribution of 
steel and its magnetic qualities, which are all different in different chronometers. 
It remains even to be proved if such lines exist for each chronometer, which 
at first sight does not appear to be necessary nor probable. The best arrange- 
ment of these experiments seems to be to change the magnet’s position successively 
by 10° or 5° (or even less where considerable changes of rate take place), and to 
keep it at a fixed distance from the centre of the balance, and not from that of 
the chronometer—for the sudden changes from FO to HO, at which Harvey 
seems to be surprised, show clearly that the balance, or its spring (probably 
both), are chiefly acted upon by the magnet. The results thus obtained would 
be comparable with each other, and would most probably show a greater regularity 
than those arrived at by Harvey. 
The last of Harvey’s Papers to be quoted (No. 12) is called forth by the striking 
fact that the same magnetic influence produced directly opposite results in the 
two chronometers B and C (p. 26). He finds the explanation of it in “‘ the varieties 
of imperfect isochronism existing among different chronometers.” 
The first part of the Paper contains some deductions, intended to show how 
fixed magnetism in the balance may be the reason why a magnet will produce 
either an increase or a decrease of the arc of vibration. Some instances will 
suffice to show his ideas. If the thermometer pieces of a balance be supposed 
to be in an active but opposite state of polarity, and if the magnetic force acts 
in the direction of the diameter joining both, with a pole opposite to the pole 
of the thermometer piece lying next, the moment the oscillations begin the 
are of vibration will be decreased, ‘‘in consequence of the effort made by the 
thermometer piece on which the magnetic force acts to approach the attracting 
pole.” And if the attractive power acts ‘‘on either side of the point of quiescence, 
within certain limits, the are of vibration will still be diminished, but in a less 
ratio than before.” And suppose, moreover, ‘‘ the direction of the magnetic 
force to pass through the centre of the balance and the limit of the semi-are 
of vibration, it is manifest, when motion is communicated to the balance, its 
effects will be to increase the are of vibration, both from its attracting one of 
the thermometer pieces and repelling the other.” If in addition to the thermo-- 
meter pieces the ares of compensation are magnetic also, it is obvious that 
the balance may be regarded as a ‘species of compound magnet,” and every 
magnetic influence, as long as it does not act at a distance equally remote from 
both poles (in which case the two effects will neutralise each other) will create 
in the balance a tendency to occupy a special position as to the direction in 
which the magnet acts, and thus an alteration of rate must of necessity occur. 
It makes, obviously, no difference whether the magnetic action is that of an 
