F. H. Bigelow — Solar and Terrestrial Magnetism. 457 



frighten off serious attacks upon its validity, and in my judg- 

 ment it has done great injury to the advancement of this branch 

 of science. There are several good grounds for distrusting its 

 truth, arid it may be stated that expert opinion is gradually 

 coming to the general conclusion that the sun, the earth and 

 the moon, are three magnetic as well as gravitating bodies, and 

 that thus several unexplained gaps in science become readily 

 filled. It is plain that while the earth is hot in the interior a 

 moderately strong magnetic held is sustained around it. This 

 fact alone makes the earth, and not a steel magnet, the analogue 

 of the sun. After the evidence brought together by van Bebber 

 in Witterungskunde, by Bulletin No. 21, and also by many 

 other writers, it is quite impossible not to accept the conclusion 

 that the variation of the sun's forces, as shown in the state of 

 its visible surface, the spots, the prominences and faculse, and 

 the corona, are synchronous with changes in all the elements of 

 the earth's atmosphere. We are therefore confined to two lines 

 of thought, either to show that there are variations in the sun's 

 electromagnetic field, that is in its insolation, or else to admit 

 that the sun possesses a true magnetic field, which embraces 

 the earth in its operations. Now there is at present no evidence 

 whatever that the sunlight field has any variable intensity, and 

 on the other hand Bulletin No. 21 shows that the earth is im- 

 mersed in an external magnetic field of such a direction and 

 strength as to make the inference necessary that its seat is in 

 the sun. Else if one admits the above-mentioned synchronism 

 between solar and terrestrial elements, it will be necessary to 

 assert that the earth's changes are sufficiently strong to disturb 

 the sun's state as observed, which is of course absurd. 



That the earth is plunged in a variable external magnetic 

 field is so simply proved as to be quite beyond controversy. 

 On Charts 17 and 18 is seen a collection of the traces of the 

 horizontal forces from the two hemispheres. They exhibit the 

 phenomenon that the horizontal force rises and falls in strength 

 simultaneously over the entire earth, which is the common and 

 persistent fact, just as much as it is true that a body falls 

 towards the center of the earth by gravitation. Likewise it 

 can be shown throughout the observations that when the hori- 

 zontal force diminishes, the vertical force increases its strength, 

 as generally and as continuously. Charts H, 7, 8, 12, 36, 37, 38, 

 39, exhibit in detail the effects upon a field surrounding a 

 magnet, when immersed in an external field of alternately 

 greater and less strength than its normal field. The closed 

 curves are expanded or contracted on each side of the mean, 

 and this involves such changes in the horizontal and vertical 

 forces as are found to be taking place throughout the earth's 

 field. I recommend that criticism begin at this point, and that 

 its consequences be candidly followed out. 



