392 Mr. Christie on the diurnal deviations, &c. 
when the directions of the needle are taken, is here clearly 
pointed out. 
The striking effects which I have seen to arise from a 
change of temperature in the magnets have certainly led 
me to adopt the opinion, that temperature, if not the only 
cause of the daily variation, is the principal. This was the 
opinion of Canton, but he could not, by it, account for the 
morning easterly variation. I might here offer some con- 
jectures on this subject, but as it is not my intention at present 
to enter fully into the general question of the cause of the 
daily variation, I will defer them, at least until I shall have 
ascertained the precise effects of changes in the temperature 
of magnets. 
