174 ANNUAL. REPOKT SMITHSONIAN INSTITUTION, 1923 



Lately, Doctor Abbot has shown that these rodlike rays, which 

 are streams of particles, restricted as to the areas from whence they 

 arise, and in the directions in which they are emitted, affect another 

 planet of the solar system. In the Proceedings of the National 

 Academy of Sciences for October, 1923, Doctor Abbot points out 

 that " when sunspots transit across the central diameter of the 

 visible disk, lower radiation values occur, and usually reach a 

 minimum on the day following the transit," and to explain this, 

 quotes the observations of Guthnick on the brightness of Saturn, 

 which indicated certain small fluctuations. These fluctuations 

 agreed in percentage with the variations of the solar constant, pro- 

 vided a time allowance was made to take account of the rotation of 

 the sun from a position facing the earth to one facing Saturn. " It 

 seemed, in short, as if rays of a certain intensity of radiation, going 

 out from the sun, rotated along with it, and so affected the dif- 

 ferent planets in the order of their heliographic longitudes." He 

 finds such ragged, unequal rays in the solar corona, and it is evident 

 that this lower radiation, about a day after a spot transit over the 

 central meridian, and a magnetic storm are both due — directly or 

 indirectly — to the same rays, for in the cases of the magnetic storms, 

 which accompanied the spots 9127 and 9143 (of the Greenwich 

 series) in February and March, 1920, the lower solar constant in each 

 case occurred about the time of greatest height of the magnetic storm. 

 The latter is due to the disturbance of the earth's magnetism by 

 the solar ray; the lower solar constant is attributed by Doctor 

 Abbot, to the diminished transparency of the enveloping ray itself. 



We therefore now recognize two distinct methods of radiation 

 from the sun; the first, general, from the entire surface and in all 

 directions; the second, special, arising from certain districts in 

 certain zones, and emitted in restricted directions only. 



Indications of variations in the general radiation have been found 

 by Doctor Abbot by higher values of the solar constant here on 

 earth, when sunspots form, or are increasing, or are brought by 

 the solar rotation into view at the east limb of the sun, and when- 

 ever the solar surface is shown by the Ha spectroheliograms to be 

 much disturbed. "When a period of quiescence in solar activity 

 occurs, the radiation values tend to fall continually until some new 

 outbreak of activity is observed." An agreement has also been es- 

 tablished between the rate of the melting of the white polar caps 

 of Mars and the progress of the solai* cycle. Thus, in 1916 

 (Monthly Notices, 76, No. 8), E. M. Antoniadi recorded that "out 

 of 21 cases of observed melting of the caps between 1862 and 1914, 

 inclusive, there are four more or less unfavorable and seventeen fa- 

 vorable to the agreement in question." 



