Beppicker— On the Influence of Magnetism on the Rate of a Chronometer. 9 
of attraction of such an iron mass.” When afterwards a magnetic bar was 
presented to a balance (which had been proved free from magnetism), the latter 
arranged itself so that the cross steel-bar was directly in a line with the magnet ; 
and, finally, two spiral springs were found to be sensibly magnetic, but their polar 
quality, though ascertained with a very light and sensitive compass-needle, and ‘‘ren- 
dered manifest in a very peculiar manner,” is, unfortunately, not detailed. Barlow 
concludes by saying:—‘‘I think it, however, highly probable that the form and 
office of the spring are precisely those most likely to create magnetism in it, and 
that when once acquired in this part of the machine, it will soon be transmitted to 
the balance itself, and consequently that there are but few chronometers which 
have been long in use that have not the balances impregnated with this subtle 
fluid, and which are therefore liable to a change of rate, more or less considerable, 
when taken on board ship or within the influence of a mass of iron.” Scoresby 
(No. 8) found ‘very sensible magnetic properties, both attractive and repulsive,” 
in seven detached chronometer balances, and adds the interesting remark: ‘ In 
some of these balances the magnetism was very strong. One, with three arms, 
had a vigorous south pole at the extremity of each ray, and a common north pole 
at the centre. The other balances had generally two poles only, but im some the 
poles of the rim were not exactly coincident with the poles of the rays.” Arnold 
and Dent (No. 17) observed that a series of freely-suspended balances adopted a 
fixed direction like a compass-needle, and found (by observing the oscillations) that 
the smaller the balance-arm, the stronger was the magnetic influence. This, of course, 
is only a consequence of the smaller weight, and therefore greater sensitiveness, of 
the balance. Wackerbarth (No. 27) remarked that the steel screw in the balance 
of a pocket chronometer had acquired strong magnetism. But by far the most 
extraordinary case is communicated by George Harvey (No. 9), which we have, 
therefore, to reproduce to a fuller extent. He observed (by means of an apparatus 
resembling that of Coulomb) the changes the intensity of terrestrial magnetism 
underwent in the neighbourhood of a chronometer. The first Table on the 
following page contains an abstract of his results. 
Similar experiments were made in the neighbourhood of the chronometer as 
well as with single parts of it, which, however, it will hardly be necessary to give 
in full. It will suffice to say, that nearly all the steel parts were strongly mag- 
netic. The inner rims of the arcs of compensation in the balance, as well as the 
steel time-screws which connected them with the transverse arm, were magnetic, 
particularly the screws, one having strong northern, the other strong southern 
magnetism. The balance-spring likewise exhibited vigorous polarity. It was 
the same with ‘the small wormed cylinders, on which the thermometer pieces 
moved.” Every screw, of which there were ten large and several small ones in 
the frame alone, the chain, the axles of the different wheels and pinions, the arbor 
of the fusee, “ exhibited the same active and permanent (magnetic) power, 
TRANS. ROY. DUB. SOC., N.S. VOL. Ill. C 
