BappicKER— On the Influence of Magnetism on the Rate of a Chronometer. 13 
magnetic meridian by S. Varley (No. 1), Northcote (No. 18), Fisher (No. 19), 
and Airy (No. 22), besides some shorter notices and experiments, of which 
those of Arnold and Dent (No. 17) are especially to be mentioned. Experiments 
with soft iron are made by Peter Barlow (No. 6) only, and magnetic experiments 
are published by Fisher (No. 2), Scoresby (No. 8), Harvey (No. 10-13), Arnold 
and Dent (No. 17), Ansart-Deusy (No. 25), and Delamarche and Ploix 
(No. 26). Rules of precaution and for neutralising the influence of terrestrial 
magnetism are especially given by Barlow (No. 6), Scoresby (No. 8), and Airy 
(No. 22), Varley made some few but extraordinary observations of changes of 
rate in a watch, the balance of which had been found to be strongly magnetic 
(cf. p. 8, seg.) In one position, when the plane of the balance was horizontal, 
and its north pole (the balance being at rest), directed towards the north, the 
watch gained daily 5™ 35°; in the reverse position, the balance—when at 
rest—having its north pole directed towards the south—the rate in twenty- 
four hours was 6™ 48° losing; the whole difference of rate between these 
two positions thus amounting to the considerable quantity of 12" 23°. When, 
however, the steel balance was replaced by one made of gold, the rate was found 
‘‘as uniform as could be expected, the watch having a duplex escapement, but 
no compensation for the expansion and contraction occasioned by heat and cold.” 
Varley’s instance of the action of ¢errestrial magnetism upon a magnetic balance, 
and consequently upon the watch’s rate, is doubtless quite an exceptional one, and 
in no case has such an extraordinary influence been observed again; and it is 
rather fortunate, that just the first observation published showed so strong an 
effect, thus increasing the general interest in the matter considerably. But still 
it is surprising that not before 1820, or twenty-two years afterwards, these obser- 
vations were taken up again by George Fisher (No. 5), who thus gave occasion to a 
considerable number of experiments and discussions. 
Fisher was induced by his observations, detailed before (p. 2), to ascertain 
how far the alteration of rates the chronometers underwent by their being trans- 
ported on shipboard ‘could be reconciled with that observed in chronometers 
when under the influence of magnets placed in different positions with respect to 
their balances.” He made use of two watches (No. 1 and 2) with steel balances, 
and two (probably pocket) chronometers (No. 8 and 4), the latter by Arnold, and 
observed the changes of rate produced by approaching magnets of twelve inches 
in length, at a distance of two inches from the balance in four different positions 
and in the planes of the balances. The changes observed in the two watches 
‘No. 1 and 2 were very considerable ; No. 1 gaining with both poles and in every 
position of the magnet but one, the maximum being 72™ in twenty-four hours ; 
No. 2 gaining with both poles and in every position, upwards, to 21™ in twenty-four 
hours. The result obtained with the chronometers No. 3 and 4 is as follows:— 
