16 BappickeR—On the Influence of Magnetism on the Rate of a Chronometer. 
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[Perer Bartow.—Perer Lecovnr. | 
Fisher’s observations at Spitzbergen (p. 2.) and his explanation of them by 
means of the action of the ship’s iron, induced Barlow to make some experiments 
himself, in order to ascertain whether soft unmagnetized iron had actually any effect 
in changing a chronometer’s rate. He assumed that such an effect would only take 
place if the spring or some part of the balance had previously become magnetic, 
and that “accordingly as the balance was placed in this or that direction with 
respect to any given mass of iron, the rate of the chronometer would be accelerated 
or retarded, and not uniformly accelerated.” . . . ‘‘Or rather, perhaps, I ought to 
say,” he continues, ‘that a different direction of the balance would alter the are 
of its vibration from greater to less, or from less to greater; but it would still 
depend upon the original adjustment of the machine, whether the result would be 
to accelerate or to retard its action; that is to say, it would depend upon the con- 
tingency, ,whether the chronometer had a tendency to gain or lose in short ares, 
which I am informed is nearly an equal chance, if it proceed from the hands of a 
scientific workman; but that in general cases the probability is that the watch 
will lose in large arcs and gain in small ones.” 
Before I begin to describe Barlow’s experiments I reproduce the following ideas 
of Peter Lecount (No. 7) as to the influence of the ship’s iron. He, too, thinks 
that this influence is caused by a quantity of fixed magnetism in the balance and 
its spring, and considers especially the magnetism lying entirely inside the chrono- 
meter to be the chief reason of the changes of rate in different parts of the 
world. These magnetic attractions will act in different ways; for instance, 
fixed magnetism in the balance and changeable magnetism in the steel spindles, 
the rate will be changed by any considerable alteration of the dip, as by that direc- 
tion and power of the changeable magnetism will be altered. Fixed magnetism in 
the spindles and changeable magnetism in the steel of the balance will produce the 
same effect as before; and “the balance spring will likewise be acted on under 
similar circumstances.” 
These remarks of Barlow and Lecount are of very great importance. Barlow 
shows plainly the reason why a general rule holding good for all chronometers, 
as to whether magnetism must produce acceleration or retardation, cannot be 
given [cf. George Harvey (No. 12), on p. 30], and Lecount points out a source of 
magnetic disturbance of a chronometer which deserves very close attention. This 
remark of Lecount appears so much the more striking, when we take Harvey’s 
instance of magnetic intensity (No. 9, p. 9) in a chronometer into account. 
