L. A. Bauer— Variation of Terrestrial Magnetism. 109 
From these deflections the position of the node was easily 
estimated. It appears from the best results that we have 
obtained, that the velocity of short electric waves traveling 
along two parallel wires differs from the velocity of light by 
less than 2 per cent of its value. It has been shown theoreti- 
cally, that the velocity of such waves traveling along a single 
wire should be the velocity of light approximately. Our 
results, therefore, in a certain sense, confirm the theory, to an 
accuracy within their probable error. 
Theoretically too, the velocity should be approximately equal 
to the ratio between the two. systems of electrical units. The 
average of the best measurements of this ratio is 3-001, which 
is nearer the average velocity obtained by us than the velocity 
of light. 
Jefferson Physical Laboratory. 
Art. XIIl.—On the Distribution and the Secular Variation 
of Terrestrial Magnetism,* No. 1; by L. A. BAvER, PH.D. 
For the empirical results already obtained in my investiga- 
tion on this subject, I refer the reader to an abstract published 
in this Journal.t The general conclusion was that the two 
phenomena, the distribution and the secular variation, appear 
to be closely related ; they obey similar laws and seem to be 
connected in some way with the rotation of the earth. 
In the following, I intend to establish this important result 
more conclusively, adopting a method somewhat different from 
the one previously employed. I shall for the present confine 
myself solely to observations of declination and inclination, since 
reliable intensity data cover but a comparatively small interval 
of time. A collection of observations of intensity is, however, 
‘being made and will be discussed at some future date. 
Unfortunately the points on the earth’s surface where we 
possess long series of magnetic observations are not uniformly 
distributed. The consequence is that it is very difficult at 
times to interpret the phenomena observed at any special 
locality or to discern the law governing the onward progression 
of a particular phase of the secular variation. To help me 
out of this difficulty, I adopted the idea of choosing hypothet- 
* Under this title, I intend to publish a series of articles embodying and grow- 
ing out of two papers presented to the Philosophical Society of Washington, 
May 25, 1895: ‘On the Secular Variation of Terrestrial Magnetism” and “A 
Preliminary Analysis of the Problem of Terrestrial Magnetism and its Variations.” 
Both papers are abstracted in ‘‘ Science,” vol. I, No. 25. 
t+ June, 1895, p. 471. For a fuller account see ‘‘The Physical Review” for 
May-June and July-August, 1895. 
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