( 288 ) 



tlie Eartli tor the main pail to diroct niaunetic action of the Siui ; 

 lie snp})(>se.s the inaiiiietie coiKhtion ot' the Sun to I>e \ery varial)le. 

 Hut as Lord Kelvin ^) lias deiuoiistrated that the solar magnetism 

 and its ^■ariability onulit to he enormous to produce, hv direct induction, 

 these (Hsinrhances of the terrestrial niaunetism, BuiKLOW also admits 

 a \ariahle generation of elect i-icity in the higher layers of the at- 

 mosphere, through the ionising action of the Sun's inconstant radiation. 

 These views of Bioklow ha\e heen analysed and criticised by Schuster'-'). 



x\ll these theories fail in one important point. Indeed, the meteoro- 

 logical and earth-magnetic disturbances generally manifest themselves 

 in such a manner that they cannot be considered sim})ly an increase 

 or decrease of iioi'iual activity. F(»r instance in the case of magnetic 

 storms, the disturbance-x'eclor is enlii'ely out of keeping with the 

 normal daily variations. The ca|)i-icions origination and course of the 

 barometric depressions, which play s(» prominent a |>art in deter- 

 mining the weather conditions in many parts of the globe, cannot be 

 explained as mei'ely resulting fiom increased oi-dinary atmospheric 

 circulation; and many more examph'^ might l»e a<lded to these. 



We must therefore consider the natiiiv of the cosmic influence to 

 be such, that, although emanating from the Sun and striking the 

 Earth within cones whose 0|)ening is only 17,(V' wide, it notwith- 

 standing acts very (HlfcM-enlly in the \arions regions of the globe. 

 Moreover, this influence distinctly shows a semi-annual periodicity. 

 As yet no theory, based on the conce|»tion of a variable solar out|nit, 

 has lieen found to account for these striking charcicteristics of the 

 cosmic influence. 



If then, in order to explain the iieriodicity of solar phenomena, it 

 has not been necessary to admit a varying activity of the Sun, we need 

 not be deterred from acce[)ting this conclusion by the consideration 

 that it iini»lies the abandoning of all prexailing ideas as to the 

 influence of the Sun's acti\ ity on meteorological disturbances. 



2. Effects of the in ore incut of the Earth throu(/h the 

 IrreqvJar pehl of the Sun's rad'mtion. 



When the rays of the Sun fall through a piece of ordinary window- 

 glass on a distant screen, we notice an irregular distriLtution of 

 light. In the same manner we imagine the rays ])roceeding from the 

 inner parts of the Sun, after traversing the outer and thinner layers, 



1) Lord Kelvin, Nature 47, p. 107^110. (1892). 



2) Schuster, Terrestrial Magnetism 3, p. 179—183. (1898). 



