212 ANNUAL REPOET SMITHSONIAN INSTITUTION^ 1913. 



terrestrial magnetism, as in the biological sciences, must surely be 

 the study of the variations and mutations ! 



Is it not probable that the very features of the earth's magnetism 

 regarded at one time as defects — the "constant inconstancies," as 

 an earlj^ writer quaintly put it — will instead become sources of help 

 and inspiration from totally different points of view or in some 

 entirely different line of thought? Who knows of what import the 

 riddles of the earth's magnetism, characterized by eminent physicists 

 as being, next to gravity, the most puzzling of natural forces, may 

 be, not simply to the magnetician alone, but to all interested in the 

 steady progress of the physical sciences? Thus Schuster suggests 

 that " atmospheric electricity and terrestrial magnetism, treated too 

 long as isolated phenomena, may give us hints on hitherto unknown 

 properties of matter." " The field of investigation into which we 

 are introduced," says Maxwell, "by the study of terrestrial mag- 

 netism, is as profound as it is extensive." And, says Sabine, one of 

 England's greatest and most enthusiastic magneticians, " Viewed 

 in itself and its various relations, the magnetism of the earth can 

 not be counted less than one of the most important branches of the 

 physical history of the planet we inhabit." 



