BeppicKER—On the Influence of Magnetism on the Rate of a Chronometer. 23 
(practically) is never equal to the earth’s magnetic force, and the earth’s magnetic 
force will never be doubled by the addition of the ship’s force. Therefore if the 
earth alone will not sensibly affect a chronometer, the earth and ship together will 
scarcely disturb it sensibly.” The other remark was made by the Astrono- 
mer Royal in 1859, and is to a similar effect (cf. Wackerbarth, No. 27), viz. : 
‘that, with very rare exceptions, the effect of the earth’s magnetism, which is 
much greater than that produced by local attraction, is wholly insensible.” In 
spite of these remarks of the Astronomer Royal, the question of the ship’s influ- 
ence upon a chronometer cannot yet be considered to be solved, and further experi- 
ments seem to be highly desirable. These would most probably lead now to a 
final result, since the theory and practice of compass deviation have reached such a 
high degree of perfection in our days. 
Scoresby made some experiments in order to see how far the magnetic in- 
fluence might be general, and found that in three watches subjected to the action 
of magnetism a change of rate took place whenever a change was made in the 
relative position of the watch and the magnet. This leads him to the following 
consideration. Had any of the balances been free from magnetism, its rate (in all 
horizontal positions) would have been uniform, ‘‘ whether under the action of 
terrestrial or of moderate artificial magnetism,” for there would have been only 
induced “transient” magnetism in the balance, the poles of which change with 
every change of position of the watch, so that the rate would be unaffected by any 
slight magnetic influence. But in the case of a permanent magnetic quality of the 
balance, ‘‘there would be a repulsive action of the magnet in some positions and 
an attractive in others, which, affecting the vibrations of the balance in different 
ways, might be expected to produce a change.in the rate of the watch.” The 
only difference between these effects, whether produced by terrestrial magnetism 
only, or by artificial magnetism (directed in a similar way), was presumed to be in 
quantity. 
The experiments with one watch only are communicated. A bar magnet, 
12ins. long, was placed in the magnetic meridian, and the watch (which was 
remarkable for the beauty of the movement and the uniformity of its rate) was 
placed in the same line at a distance of 4 ins. from the magnet. The following 
rates were then observed:— 
When figure XII. was directed towards— 
North, the chron. lost 13° in 2° 18", being at a daily rate of — 135° losing ; 
Sai, Nl seh gammedll Quint 2") 12™, » \,; an) top yt tlok gaming; 
North, ,, 4, lost as in the first instance, but at a rate somewhat less ; 
South, ,, ,, gained 56° in the course of the night, being at a daily rate of 156° 
gaining. This acceleration above its former rate was 
probably owing to the diminution of temperature. 
