36 Bappicker—On the Influence of Magnetism on the Rate of a Chronometer. 
Here is to be remarked, that in the single observations these differences are 
hardly conspicuous, as the rate of the chronometer is altogether not very regular, 
and the temperature not as equal as could be desired. A further objection to these 
experiments—which do not offer any new features—is their arrangement, since 
the position has not been changed in the succession N., E., 8., W.; and 
finally, the intervals of observation in each position vary too considerably. They 
are, for instance, during the first set: Worth 4, 7, 5, 4, 8 days, and South 7, 4, 6, 
4 days, and greater irregularities still take place during the east and west obser- 
vations. In all these experiments it appears advisable not to make the intervals too 
long, for then the magnetic effect would be very easily obscured by other influences 
upon the rate; and, on the other hand, too short intervals are equally objection- 
able, since the changes may be gradual, and thus may not have reached their 
maximum values at the end of the interval. An interval of one or two days 
between two positions seems to be the best average, which, of course, is strictly to 
be adhered to in all the four positions. The temperature, of course, must be kept 
throughout at the same height as much as possible. 
As an appendix to Fisher’s Paper some observations of 8S. G. Northcote 
(No. 18) are given, made on H. M. 8. “Jupiter,” in 1835 and 1836, in order to 
ascertain if the chronometers showed any change of rate simultaneously with a 
change of the ship’s course. These observations are too few, and too vague to ad- 
mit of any conclusion as to the changes of rate; and it does not appear at all pro- 
bable that the irregularities in the rates are due to magnetism, since temperature 
alone would be more than sufficient to produce them. Besides, of the three chrono- 
meters mentioned, one seems to have a tendency to gain and the two others an incli- 
nation to lose independently of the ship’s course. I do not consider it necessary to 
reproduce Northcote’s few observations in full; but I repeat, how much importance 
such observations, if made systematically, would have. They could be very easily 
made along with the necessary chronometer observations ; or a simple comparison 
of the ship’s journals alone would probably lead to some results.* 
By 
iG. Bo-Amyi). 
Airy’s Paper (No. 22) is of special interest and importance, on account of the 
striking instance of changes of rate with changes of position which it contains, 
and on account of the rules for compensating these irregularities, which Airy bases 
upon his observations, and the efficiency of which he proves. 
The chronometer was Brockbank’s, No. 425, which was more subject to mag- ~ 
netic influence than any other chronometer tried at Greenwich. It had been sent 
* Similar remark by Dr. Carl Borgen on p. 800 in No. 29. 
