Polytechnic Association Proceedings. 979 



is the governing cause, the line of attraction being from the sun's 

 center to the center of the earth.* It will be seen at once that in 

 the earth's revolution round the sun, or with the sun round any 

 other center, her axle, on which she performs her daily revolution, 

 does not and cannot lie in a line with the line of attraction from 

 center to center, but must lie at an angle to it. And hoAv is thi.>? 

 If we draw a line from the North pole to the South polar axlr, 

 through or over the Atlantic ocean, and parallel to th^ earth's 

 axis, we find that the North magnetic pole lies west of such line at 

 an angle to it, and the South magnetic pole lies east of such line 

 at the same angle to it, and the result so far answers to the theor}-. 

 But here we meet with difficulty; for if the earth's revolution round 

 the sun should be the cause of polar attraction, the line of attrac- 

 tion being at an angle to the earth's axis, then because one body 

 revolving about another bod}' also in motion gains one revolution 

 of the body around which it revolves, therefore the magnetic pole 

 should revolve about the North pole once in every year, which it 

 does not. Again, we have another difficulty — the earth does not 

 revolve about the sun with etiher pole turned towards him; but 

 the tropical zone is forever turned towards the sun, and never the 

 polar regions; and the line of polar attraction is seen to be at a 

 wide angle to the line of the sun's attraction. Confirmatory o£ our 

 theor}', however, there is an inferior polarity in the Indian ocean, 

 north of the equator, sufficient, in passing over it, to disturb the 

 needle; and another in the Pacific ocean, south of the equator, the 

 two at about the same angle to the equator, as the North and South 

 poles to the earth's axis. These polarities may answer to the sun's 

 attraction, and the two, that is to sa^^, the equatorial polarities and 

 the North and South magnetic poles are, as I believe, traveling 

 together in perfect unison with each o'ther. The South Pacific 

 polarity was, I think, discovered by Captain Cook, and has, since 

 its discovery, as laid down by him, njoved some twenty or more 



* We make no question here of the laws of gravitation as demonstrated by Newton, or 

 the character or degree of its force, which is always directly at the masses of the heaveni- 

 bodies, and inversely as the squares of their distances; the only question is the identi v 

 of the gravitating force with the magnetism which directs the needle to the pole, by what- 

 ever name we designate either. It is worthy of remark here, that Mr. Barlow, in his 

 experiments to correct the influence of iron in the ship on the compass, found that the 

 attraction of iron on the magnet was of the same force and character as the "attraction 

 of gravitntion," nlthough he does not appear to have observed it himself. He found that 

 a hollow globe of thin iron had the same influence on -the magnet as a solid globe of the 

 same surface dimensions. In other words, he found the attractive force to be directly as 

 the mass, and inversely as the square of the distance. 



