388 Mr. Christie on the diurnal deviations of the 
afterwards at N i° 20' W. On cold water being poured on 
the magnets, they now only recovered their power so far that 
their forces were very nearly equal to the terrestrial forces, 
since the needle appeared to have little or no directive power 
either at north or at south : it would bear almost any degree 
of agitation at several positions within 3 0 or 4 0 on either side 
of these points. On the following morning at seven o’clock 
the magnets had recovered rather more power, the needle 
then pointing N 9 0 io' E. 
In these observations the effects of increase of temperature, 
in diminishing the power of the magnets, are most decided, 
and certainly much beyond what could have been anticipated 
from the experiments of Canton. The greatest change of 
temperature which these magnets underwent, could not 
exceed that to which his were subjected, and the power 
exerted on the needle by his, must have been fully equal to 
that of the magnets here made use of. The angle at which 
the forces were exerted, in the one case or the other, would 
have an effect, but not, as appears to me, equal to the diffe- 
rence in the deviations in the two cases. On this, however, I 
cannot speak decidedly, as I can at present only refer to the 
abridged account of his experiments. Another difference in the 
effects which took place in the two cases is, that after some 
hours, the magnets, which Canton made use of, recovered 
their power ; whereas, in the present instance, a considerable 
portion appeared to be permanently destroyed, although in 
the case of those applied to the compass No. I, they were not 
subjected to a heat by any means so great as those were which 
he employed, since the temperature of these could never have 
exceeded ioo° Fahrenheit. After sixteen days, they now 
