II. TWO of the most characteristic features of the earth's magnetism are the non-coincidence of the magnetic and geographic axis, and the secular variation. While a theory which is to claim any degree of completeness must account for these, one cannot resist the temptation of searching for any sort of phenomenon capable of giving a field of the order of magnitude of the earth's field in the hope that if such be found it may serve as a possible basis on which to build a more complete theory.