314 L. A. Bauer— Variation of Terrestrial Magnetism. 
ART. XXXV.—On the Distribution and the Secular Vari- 
ation of Terrestrial Magnetism, No. LI ;* by L. A. BAUER, 
imiee BP ; 
As stated in the preceding number, the special object of this 
communication is to see whether we can refer the secular 
varration to the secular shift of the secondary magnetic dip 
poles revealed when considering the phenomena of the distri- 
bution of terrestrial magnetism.t+ 
If this be the case, its importance cannot be overestimated. 
The investigation of the phenomenon which has been the 
source of such perplexity for several centuries—the so-called 
secular variation, whereby remarkable changes occur in the 
distribution of the earth’s magnetism in the lapse of time—has 
then entered upon a new stage; for the prime reason that we 
can now refer the secular variation to shifting magnetic poles 
that are nearly on the equator and, hence, in a region easily 
accessible, and in which magnetic observations are continually 
being made, instead of to magnetic poles in the polar regions 
where observations are rarely made on account of the difficulty 
of access. 
The magnetic charts published from time to time can repre- 
sent the distribution in terrestrial magnetism in the equatorial 
regions fairly well, while that in the polar regions must be 
more or less guess-work. Hence, the difficulty of locating 
approximately the secondary magnetic dip poles is a minimum 
in comparison with the assignment of position of those we 
believe to be in the arctic and antarctic regions. 
It behooves us then to look carefully into the matter form- 
ing the chief subject of our present inquiry. The problem to 
be solved I shall state as follows: 
What is the secular motion of the secondary magnetic dip 
oles ? 
7 Before entering upon the discussion of this question it will 
be desirable to state that all the conclusions thus far have been 
obtained empirically. No theory has been advanced. My 
purpose hitherto has been to accumulate facts to serve ulti- 
mately as a foundation upon which to base a theory. A 
sufficient number of empirical laws and facts have now been 
derived to justify and to make desirable the undertaking of a 
theoretical attack, to be begun in the following number. The 
results to be given in the present paper are still free from 
theoretical assumptions. They are facts of pure observation. 
* The main results of this paper were presented to the Washington Philosophi- 
cal Society, May 25, 1895. Abstract in Science, June 21, 1895. 
+ This Journal, Art. XX, September, 1895. 
