P OL TTECHNIC A SSOCIA TION Pr CEEDINGS. 9^7 



brought into contact. The loadstone is only such a substance, to 

 which magnetism has a strong aiBnity, and which has therefore the 

 power of absorbing and retaining longer than any other known 

 substance the ma2:netism it has received. 



Both magnetism and electricity may be excited to activity by 

 motion or revolution. Everybody has seen electricity excited by a 

 revolving machine, and if you stand under a revolving belt in a 

 manufiictory, you will feel magnetism enough to raise the hair on 

 your head; but no one will for a moment suppose that either mag- 

 netism or electricity is created by these motions — they are simply 

 roused from inactivity, as latent heat is rendered active by motion, 

 concussion, or attrition. The difference between the two I conceive 

 to be, that the force of electricity is eccentric, diffusive and 

 equalizing; that of magnetism is concentric — attracting to the 

 center. 



From all the phenomena which I have been able to see or 

 observe, I have come to the conclusion that what we call polar 

 magnetism is the result of a magnetic force, rendered active by 

 revolution. As before stated, the force is concentric, attracting to 

 the center. It is, therefore, centripetal, and, considered as a uni- 

 versal principle of nature, it identifies itself with that force which 

 astronomers call the " attraction of gravitation," a force known to 

 exist, but for which no satisfactory cause has ever been assigned; 

 and we are here led to ask, what is that force, if it be not mag- 

 netism ? By whatever name it may be called, we believe it to be 

 the same force which directs the needle to the pole, and which we 

 habitually call "magnetism." That it is 'a natural force derived 

 from a latent principle, and put in motion by a forward revolution, 

 I think fairly deducible from what is well known to every astrono- 

 •mer, viz: that the magnetic attraction, or " attraction of gravitation," 

 call it by what name we please, in revolving bodies is the opposite 

 of that centrifugal force created by their revolntion, and always 

 equal to it. And since the motion of the heavenly bodies is some- 

 times faster and sometimes slower, as proved by Kepler's law, that 

 in passing round their elliptical courses, they pass over equal areas 

 in equal times, therefore the centrifugal force created by their 

 motion is sometimes greater and sometimes less, which must alwa^'s 

 be met by an equal development of the opposite and concentric 

 force to keep the planet in her orbit. And it is well known that 

 such development is always obedient to the rate of motion of the 

 body revolving. It is evident, therefore, I think, that the activity 

 [Inst.] 62 



