PHILOSOPHICAL 
T R A N S A C T I O xN S. 
I. On the effects of temperature on the intensity of magnetic forces ; 
and on the diurnal variation of the terrestrial magnetic inten- 
sity. By Samuel Hunter Christie, Esq. M. A. of Trinity 
College, Cambridge, Fellow of the Cambridge Philosophical 
Society : of the Royal Military Academy. Communicated by 
the President 
Read June 17, 1824. 
In the paper on the diurnal deviations of the horizontal 
needle when under the influence of magnets, which the 
President did me the honour to present, I stated that these 
deviations were partly the effects of changes that took place 
in the temperature of the magnets ; and that although the 
conclusions which I drew from the observations respecting 
the increase and decrease of the terrestrial magnetic forces 
during the day w'ould not be materially affected, it was my 
intention to undertake a series of experiments for the pur- 
pose of determining the precise effects of changes of tempe- 
rature in the magnets, so as to be able to free the observa- 
tions entirely from such effects. 
These experiments vs^ere immediately made ; but I was in- 
duced from some effects which I observed, to carry them to 
B 
MDCCCXXV. 
