280 Prof. Norton on Molecular Physics. 



annual rate of the secular variation of declination in this country 

 reached its maximum about the year 1855, and that this is near 

 the maximum epoch of the secular period of the sun's spots. 

 In Europe the tendency of the same general cause is to make the 

 secular rate the least at the same epoch. In this way probably 

 it has happened that the increasing secular rate of the easterly 

 movement there has become nearly constant*. 



Observation has furnished the means of testing the explana- 



* From our present stand-point we may obtain a distinct view of the 

 origin of the diverse luminous phenomena of the aurora boi ealis, as well as 

 of the attendant magnetic phenomena. We may perceive that the aurora 

 is a combined magneto-electric and electromagnetic phenomenon; that the 

 auroral light results from electric discharges along the lines of magnetic 

 polarization that traverse the masses of solar matter while passing over 

 from the preceding to the following side of the earth's photosphere; that 

 the discharges are in a great degree due to the demagnetizing action of the 

 electric currents developed by the solar matter impinging upon the prece- 

 ding side of the photosphere, but in part also to a direct disturbance of the 

 electric equilibrium along the lines of polarization by these currents or by 

 the free electricity in the photosphere. We here allude especially to the 

 more conspicuous auroras. It is conceivable that, should there be an in- 

 termission in the reception of auroral matter from the sun, or the supply 

 feeble, the currents continually excited in the earth's crust by the aether 

 of space may, by augmenting the intensity of the earth's magnetism, origi- 

 nate currents in the photosphere directed upward instead of downward. 

 Such effects should be especially observable in the regions of greatest di- 

 rective force. It is to be observed that the tendency of the demagnetizing 

 action accompanying the more conspicuous auroras, with the attendant 

 electric currents, is to disperse the auroral matter, and in this way to occa- 

 sion its expulsion to an indefinite distance, under the operation of the repul- 

 sive force of the earth exerted upon single molecules or minutely divided 

 masses (see Silliman's Journal, vol. xxxviii. p. /0). The decrease of the 

 earth's magnetizing action cooperates in this. 



There are several important probable inferences that may be drawn 

 from the preceding discussion, which it maybe advisable to state here very 

 briefly. 



1. The sun must have become magnetized after the same manner as the 

 earth, by reason of its rotation, and of its motion of rotation combined with 

 its progressive motion through space. As in the case of the earth, there 

 must be a continual development of new currents tending to exalt its mag- 

 netic state. These new currents, by this mode of action, should condense 

 the auroral matter of the photosphere along the lines of polarization, and 

 so develope both light and heat. The spots on the sun are probably due 

 to an inverse effect (that is, demagnetizing and dispersing) produced by 

 the electric currents directly developed in the photosphere, by the descent 

 into it of cosmical matter as the sun moves forward in space. According 

 to this, the faculse and accompanying dark spots have a similar origin to 

 terrestrial auroras. Upon this theory, the dark spots should be wanting at 

 the magnetic equator and at the poles. They should also be mostly con- 

 fined to low latitudes (heliographical). 



It is probable that a large fraction of the heat by which the temperature 

 of the body of the sun is maintained is the result of the continual recur- 

 rence of the process of magnetization by the impinging action of the aether 



