OP THE MAGNETIC DECLINATION. 
511 
benefit for the advancement of the science of terrestrial magnetism; and I hope I have 
been successful in showing that for such a purpose it is not enough to inquire into the 
nature of the luna, -diurnal curve variations only for the time of the moon’s farthest 
deviation from the equator, as has in several instances been the practice. It is indeed 
indispensable for theexact investigation of themoon’s influence on the magnetism of our 
eaith, to extend the method of inquiry, which I have just explained in the example of 
e magnetm decimation, to the other magnetic elements, for the lunar-diumal variation 
of he horizontal force also shows great differences according as the moon is to the 
north or the south of the equator. As far as my researches have as yet gone, I feel 
whew h 'ft reSUltS ” tUS ktter ° aSe are at leaSt ei » uall y with those 
which have made the immediate subject of this short paper. As soon as the respec 
ive discussions are brought to a close, I shall not fail to communicate the results of my 
labours in this direction to the Royal Society. 
MDCCCLXVIl. 
