BappicKER— On the Influence of Magnetism on the Rate of a Chronometer. 29 
One fact, however, of great interest, to which Harvey also directs special 
attention, is set forth by his experiments. It is the immediate effect of the 
magnetic influence—in many instances Harvey observed the changes of rate to 
take place suddenly from considerable acceleration to considerable retardation, 
and vice versd—and the ‘‘ freedom” with which the influence was lost when the 
magnetic action was reduced or altogether removed. This is particularly striking 
in the case of chronometer A, where there is a remarkably small difference 
between the detached rates before and after the experiments, though the magnet 
was of considerable power and brought very near the time-piece. We conclude 
from this with Harvey, that the influence of a magnet is often only transient, 
and that a magnet does not easily- impart its magnetism sensibly to the steel 
parts of a chronometer. 
I have now briefly to consider Harvey’s discussion of the behaviour of 
chronometer A (No. 13). 
In the figure we copy from Harvey (Plate I., Fig. 10), the lines OA, OB, OD, 
OE, OF, OH, OK, OL, denote the directions in which the magnet was applied to 
the chronometer A, as represented by the corresponding figures 1 to 8. Thus LO 
is the line of the greatest observed acceleration, as HO that of the greatest 
retardation of rate; and further on we have: rate KO : LO :: DO: EO, as 
remarked before. Now Harvey considers it probable that between BO and DO 
there should be one direction, where the magnetic influence would have produced 
a rate nearly equal to the detached rate of + 20°4: similar directions are likely 
to exist between FO and HO, HO and KO, and finally LO and AO. These 
‘‘lines of detached rate”? he determines under the assumption that a propor- 
tionality such as that mentioned above might exist throughout, and finds thus the 
approximate positions of the lines of detached rate CO, GO, IO, and MO, as 
they are drawn in the figure. 
He considers it rather remarkable, that there is very nearly rate KO + AO 
= LO; and further on, that CO and TO are very nearly a straight line, and 
that also GO and MO are very nearly a continuation of each other. 
Harvey then proceeds to find out the rate of acceleration or retardation for 
each degree of each arc on the same hypothesis of proportionality as he used above. 
I do not think it necessary to reproduce his results. 
The basis of this discussion, the proportionality of rates, is admittedly a very 
uncertain one. For it is by no means necessary, nor—considering the want of 
symmetry in the distribution of steel in a chronometer, and the excentric position 
of the balance—even. probable, that such a proportionality, though observed in 
some directions, must exist throughout. The “lines of detached rate” are, 
therefore, equally uncertain. It is, however, very interesting to determine 
experimentally their position, which is probably peculiar to each individual 
chronometer. For these lines are those directions in which the united actions 
