( 287 ) 



If, therefore, spots and faculac are iiol in themselves tlie factors 

 wliich l>_v their |ie(*iiliai' racUatioii of ii,i>hl and heat cause the sii|»|)()secl 

 llnctnations in the output of sohir cneruv, it nii,i>ht he expected that 

 entirely different agencies |>lav tiie most conspicuous part in tiie 

 production of the phenomena un(h'i- consi(h'ratiou. 



In tliis sense Arkiik.nu s ' ) has started an hypothesis in which the 

 latest discoveries in coiuiexion \\ ith tlie kathodic rays, the ionisatioii 

 of gases, the proj)erties of ions and eh'ctrons and tlie pressure of 

 radiation liave been inlro(hiced. He atlriliutes ihe said periodical 

 [)hen()mena on Earth to sohii' matter, charged with negati\e electricity 

 and h(>ing propelled from the Sun's surface by certain centres of 

 acli\ity there present (thus accounting for tlie jtei'iod of 25,929 days). 

 The amount of electricity thus generated varies with die Sun's 

 activity, it being greatest at maxima of s[)Ot freipiency. This solai- 

 matter is scattered through space by the pressure of radiation and 

 causes the higher layers of the terrestrial atmosphere to be chai-ged 

 with negative electricity. l>y the discharges kalhodic rays and 

 })olar lights are pi-oduced ; the electritied jtarticles, cai-ried along by 

 the wind, h)rm electrical cui-i-ents which disturb the magnetism of 

 the Earth. 



Several i)oints of this theory have been criticised by Ch. Nokdm.\nn^), 

 Avilo oifers an entirely dilferent explanation for the xariable inlluencc 

 of the Sun on meteorological phenomena. He ascribes it to /oik/ 

 I'lt'ctriciil irarcs, sent out by the Sun, more jvarticularly in the regions 

 of s()ots and taeniae, and at times of maximum s|)ot frequency. 

 Wliene\er these Heilzian waves ])enetrate into Ihe higher layers of the 

 almos[)here, they increase their conductivity and render them luminous. 

 \\\ this manner he accounts for the fact that during spot maxima 

 stronger electrical currents are present in Ihe atmosphere, magnetic 

 \arialions are more marked and [)olar lights more freipient and intense. 



Ihit we have seen before that neither important magnetic 

 disturbances nor intense |)olar lights invariably accompany \"ery 

 conspicuous solar phenomena. Xokdmann's theory ihei'cfore requires 

 the admission of the existence on the solar surface of separate 

 emission centres of long electric waxes, independent of spots and 

 taeniae. This hyjiothesis does not sinqilify our coiic(»ption of the 

 constitution of the Sun. 



BiGKLOW^) ascribes the inlluence of the Sun on die maunetism of 



1) AuRHENius, Rev. gen. «I. Sc. 13, p. (i.")— 7(1; Leiuli. d. kosm. JMiysik, S. 1 V.» 155. 

 -) Cii. XoRDMAXX, llev. gc'-n. d. Sc. p. 37'.)— )i8!S. 



'■'•) BuiKUJW, Solar and Toiicsliial Magnptism, II. S. Woalli. liur. Ijiillotin No. :21, 

 1898; Eclipse Meteorology and Allied Problems. Washington 190^. p. 1U4. 



