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THE 
AMERICAN JOURNAL OF SCIENCE 
[THIRD SERIES.] 
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Art. XX.—On the Distribution and the Secular Variation 
of Terrestrial Magnetism, No. LT ;* by L. A. BAvER, Pu.D. 
In the present communication it is the intention to endeavor 
to localize the chief cause of asymmetry or distortion in the 
earth’s magnetic field. in asubsequent paper a similar attempt 
_ will be made with respect to the secular variation. 
How shall we formulate our problem? We do not as yet 
know conclusively whether the earth 1s a magnet or an electro- 
magnet—i. e., whether the earth acts upon a freely suspended 
magnetic needle as a permanently magnetized body, with 
definite magnetic poles or centers of attraction, or whether it 
acts like a soft piece of iron rendered temporarily magnetic by 
a current of electricity circulating around it. To put the 
matter tersely, no satisfactory answer has as yet been given to 
the question : “Ts the earth’s magnetism permanent or 
induced ?” 
A priori one might be led to the latter opinion. For if 
_we recall that the intensity of the magnetization of the earth 
can be easily compared with that which we produce with great 
difficulty in steel magnets and consider the force necessary to 
increase the magnetization or diminish it, it would seem that 
the mighty disturbances, termed magnetic storms, which at 
times simultaneously affect the whole geomagnetic field, would 
not so readily result if the greater part of the earth’s field were 
in a permanent state. We must have apparently a more sensi- 
tive tield—one readily susceptible to change. 
Peter Barlow in reviewing Biot’s, Kraft’s and his own 
researches in 1831 arrived at the following conclusions :—t 
* See foot note to No. I in Augustnumber of this Journal, Art. XII., p. 109. 
+ Phil. Trans. Roy. Soc., 1831, Art. VI., p. 102. 
Am. Jour. Sci1.—THIRD SERIES, Vou, L, No. 297.—SEPTEMBER, 1895, 
