270 Prof. Norton on Molecular Physics. 



matical exposition was given of the formal relations subsisting 

 between the principles of magnetism and heat in the crust of the 

 earth, based upon certain mechanical ideas. We have already 

 seen (p. 267) that the fundamental ideas then assumed are in 

 essential accordance with the present theory of the origin of 

 terrestrial magnetism. It may now be added that the mathe- 

 matical relations shown to subsist between the intensity of the 

 magnetic action and the temperature may be seen to have a 

 physical basis. The dependence here alluded to arises from the 

 fact that the electric currents developed by the impulsive action 

 of the sether of space within the crust of the earth must, to a 

 certain extent, pass off in the form of heat, and that the earth 

 may derive a large portion of its heat from this source. In- 

 equalities in the mean temperature of the earth's crust at equal 

 distances from the equator should result from inequalities of 

 elevation, &c, and from variations in the intensity of the result- 

 ant currents traversing the localities. It will be readily seen 

 that if the inequalities of the mean temperature of the crust of 

 the earth resulted entirely from the heat developed by the sup- 

 posed action of the sether of space, the distribution of the tem- 

 perature and magnetism w r ould entirely correspond, that the 

 poles of greatest cold would coincide with the magnetic poles, 

 and the thermal equator with the magnetic equator. 



Periodical Variations of the Magnetic Elements. — In a pap r 

 published in Silliman's Journal, vol. xix. p. 183, the author under- 

 took to show that these variations are such as should result from 

 two supposed sets of currents traversing the photosphere of the 

 earth, or two corresponding sets of cuiTents traversing the earth's 

 crust. These currents were called respectively radial and ecliptic — 

 the radial currents radiating from the region of the photosphere 

 most directly exposed to the impulsive action of the sun's rays, 

 and the ecliptic originating on the side of the earth toward 

 the sun, and in directions parallel to the plane of the ecliptic. 

 We have now to observe- — (1) That the ecliptic currents running 

 from east to west, formerly supposed to be developed in the 

 earth's photosphere, have their counterparts in currents running 

 from west to cast in the crust of the earth, and developed by 

 the orbital motion of the earth on the side nearest the sun. 

 (2) That the orbital motion of the earth developed, within the 

 mass of the earth, currents running from east to west on the side 

 of the earth opposite to the sun. (3) The impulsive action of 

 the aether upon the forward parts of the earth, as it advances in 

 its orbit, must originate currents radiating from those regions 

 over the earth, and will especially give rise in the early morn- 

 ing hours to currents running toward the north in latitudes 

 lying to the north of the ecliptic, which will deflect the needle 



