Ba:ppicKER— On the Influence of Magnetism on the Rate of a Chronometer. 49 
iron is to be brought into the magnetic meridian ; the magnetic intensity to be de- 
termined in its vicinity by means of a compass, and the chronometer placed in such 
a way that the balance occupies the place of the compass-needle as nearly as possible. 
Then the chronometer is to be turned as before. Variations of interest and impor- 
tance could be made by putting the chronometer into places of different intensities 
(which can be varied by changing the distance or the relative position as to the 
ball), and especially by placing the soft iron in succession N., E., 8., W. of the — 
balance, and turning the chronometer through the four azimuths once in each 
position. 
The magnetic experiments which will have to follow those with soft iron will 
be similarly arranged: the soft iron is to be replaced by a magnet, and the chro- 
nometer under its influence turned through the different azimuths. The variations 
and complications desirable are naturally more numerous here, and may perhaps 
be classified under the following heads :— 
1. Relative position of the magnet as to the chronometer. 
a. The magnet is at first to be placed in the plane of the magnetic meridian 
and that of the balance. | 
b. The magnet is to remain parallel to the preceding position, but raised above 
or lowered beneath the plane of the balance. The results in these two positions as 
to the balance are likely to be different, since the spiral spring lies on one side 
of the balance (underneath). As the effects of the magnet upon the balance at 
equal distances above or below its plane would most probably be equal if there 
were no spiral spring, we have here, perhaps, a means of separating the influence 
upon the balance from that upon the spiral, inasmuch as an eventual difference 
between the effects in these two positions might be attributed to the spiral 
spring alone. This: variation of the experiments appears, therefore, particularly 
important. 
c. The magnet remaining in the magnetic meridian, but forming different 
angles with the balance plane. Here exist two specially prominent positions : 
one parallel to the needle of inclination, and the other vertical to the plane of 
the balance, above or below the centre or special points of its circumference. 
The differences of rate to be expected will be of considerable interest, being 
again partly due to the spiral spring. 
d. The magnet is to be placed out of the plane of the magnetic meridian, but 
in the plane of the balance, forming different angles with the primary direction— 
or, which is the same, the chronometer is to be kept fixed, and the magnet is 
to be shifted round through different azimuths. It would be particularly valuable _ 
to ascertain if there is any sensible difference between the magnetic influence in 
_ this and in the arrangement described under a. 
e. The distance of the magnet from the balance is rather a critical point; for 
though it is at least not very probable that a magnet will impart its magnetism 
TRANS. ROY. DUB. SOC., N.S, VOL. III. I 
