Prof. W. A. Norton on Terrestrial Magnetism. 3 



explicable manner the intensity of the magnetism of the terres- 

 trial particles ; or as bearing towards it the relation of cause and 

 effect. But there is another view to be taken of the matter. 

 We may regard the two principles of heat and magnetism as 

 similar in their ultimate physical nature, as every where subsist- 

 ing together, and that the causes which produce a variation of 

 temperature at the surface of the earth, as we pass from one point 

 to another, occasion at the same time and in like manner a varia- 

 tion of the magnetic intensity of the particles. So that the tem- 

 perature at each particular place may be taken as the approxi- 

 mate measure of the molecular magnetic intensity there. The 

 conception that I have formed of the probable physical nature of 

 the imponderables, of which I have given an exposition in a paper 

 read before the American Philosophical Society in December last, 

 has led me to take this view of the physical relations subsisting 

 between the heat and magnetism of the earth. This conception 

 is, essentially, that all the phenomena of the imponderables are 

 •but different effects of different vibratory motions of the particles 

 of matter, and of the ethereal undulations produced by these vi- 

 brations ; — the vibrations answering to the different principles of 

 light, heat and electricity, differing in time and intensity, and pos- 

 sibly in some instances in direction, of vibration. Agreeably to 



this general theory I conceive each particle of the earth's mass to 



be the centre of a system of undulatory movements propagated 

 through the surrounding ether, and of every variety of time and 

 intensity of vibration within certain limits. To the waves or 

 pulses of feeblest intensity and shortest time of vibration I at- 

 tribute the phenomena of magnetism ; or, at all events, I suppose 

 the waves of magnetism to lie at the opposite extreme from the 

 waves of heat. It thus happens that all the particles of the mag- 

 netic needle receive the impulsive actions of the waves of mag- 

 netism propagated from the particles of matter at the earth's sur- 

 face, and at certain depths below the surface ; — from how great a 

 depth will depend upon the degree of transparency, to the j 

 waves, of the matter of the earth. Thai the principle of mag- 

 netism is incoercible, or that it passes freely through opake bodies 

 of ordinary thickness, has been fully established by the experi- 

 ments of M. Haldat : and that all the particles of die magnetic 

 needle are subject to the action of the magnetic force of the earth, 

 is evident from the fact that the directive force of the needle is 

 proportional to its mass. Why it is that magnets alone are sensi- 

 bly influenced by the impulsive actions of the ethereal pulses, I 

 cannot now stop to consider. These theoretical views, I do not 

 here present for the purpose of advocating them, but simply be- 

 cause they furnish a simple and comprehensive conception of the 

 terrestrial magnetic forces and of their relations to the earth's tem- 

 perature. The mechanical theory of terrestrial magnetism which 



