METEOROLOGY OF TEE SJJN AND EARTH. 85 



upon the sun-period, but its amount is very small, whereas the varia- 

 tion in cyclonic disturbance is very great. We are thus tempted to 

 associate this cyclone-producing iufluence of the sun with something 

 different from his light and heat. As far, therefore, as we can judge, 

 our luminary would appear to produce three distinct effects upon our 

 globe. In the first place, a magnetic and meteorological effect, de- 

 pending somehow upon his rotation ; secondly, a cyclonic effect, de- 

 pending somehow upon the disturbed state of- his surface ; and, lastly, 

 the well-known light and heat effect with which we all are familiar. 



If we now turn to the sun, we find that there are three distinct 

 forms of motion which animate his surface-particles. In the first 

 place, each particle is carried round by the rotation of our luminary. 

 Secondly, each particle is influenced by the gigantic meteorological 

 disturbances of the surface, in virtue of-which it may acquire a veloci- 

 ty ranging as high as one hundred and thirty or one hundred and 

 forty miles a second ; and lastly, each particle, on account of its high 

 temperature, is vibrating with extreme rapidity, and the energy of 

 these vibrations communicated to us by means of the ethereal medium 

 produces the well-known light and heat effect of the sun. 



Now, is it philosophical to suppose that it is only the last of these 

 three motions that influences our earth, while the other two produce 

 absolutely no effect ? On the contrary, we are, I think, compelled, by 

 considerations connected with the theory of energy, to attribute an 

 influence, whether great or small, to the first two as well as to the 

 last. 



We are thus led' to suppose that the sun must influence the earth 

 in three ways, one depending on his rotation, another on his meteoro- 

 logical disturbance, and a third by means of the vibrations of his 

 surface-particles. 



But we have already seen that, as a matter of fact, the sun does 

 appear to influence the earth in three distinct ways one magnetically 

 and meteorologically, depending apparently on his period of rotation ; 

 a second cyclonically, depending apparently on the meteorological 

 conditions of his surface ; and a third, by means of his light and heat. 



Is this merely a coincidence, or has it a meaning of its own ? We 

 cannot tell, but I may venture to think that, in the pursuit of this 

 problem, we ought to be prepared at least to admit the possibility of 

 a threefold influence of the sun. 



Even from this very meagre sketch of one of the most interesting 

 and important of physical problems, it cannot fail to appear that while 

 a good deal has already been done, its progress in the future will very 

 greatly depend on the completeness of the method and continuity of 

 the observations by which it is pursued. We have here a field which 

 is of importance not merely to one, or even to two, but almost to every 

 conceivable branch of research. 



Why should we not erect in it a sort of science-exchange, into 



