PROCEEDINGS OF THE CANADIAN INSTITUTE. 107 



couditiou gives hot or cold seasons to the earth. If from any cause the sun did 

 emit more heat one year than another, the tirst eflect, it seems, would he the 

 expansion of his own visible disc. Nor does the answer given by Schmidt, of 

 Stuttgart, make this objection less weighty, whose work of 1891 has been recalled and 

 further explained by Otto Knopf, of Jena, in 1893. They do not think that the 

 light reaches us from the solar surface ; in a word, they deny that there is a 

 definite surface to the sun. They say his light originates within a globe of super- 

 heated gases and that, owing to the refractive index of these gases being reduced 

 tbrough diminished density as the external strata are reached, the rays from within 

 the sphere necessarily appear to be limited by a circle. They think the spots are 

 not upon what looks to be a photospheric surface, but below it, and even suggest 

 that they may be optical phenomena due to disturbances of the refracting 

 properties of the superior layers. Their theory of the spectrum is necessarily 

 unusual too. The solar spectrum was long supposed, following Kirchoff, to 

 originate on the photosphere, which he considered liquid, and covered by an 

 atmosphere which by absorption caused the well-known dark lines. Schmidt and 

 Knopf think the violet and blue rays originate in a smaller concentric shell tlian 

 the red rays, under greater pressure, and that having to pass through a denser 

 medium throws them farther along the spectrum.' The visible circumference of 

 the sun being unreal, the absorption lines may have their origin at a considerable 

 depth within the solar atmosphere, which they think is so rare in the shells 

 outside the incandescent strata as to have very little absorptive effect. 



That the sun does emit more heat at certain periods than at others, varying 

 according to the extent of spots upon his surface, seems to be the opinion of the 

 day, though our own Canadian records do not indicate the slightest periodicity, 

 excepting in so far as rain-fall is concerned (where there is a certain periodicity 

 which may be due to heat elsewhere). But there is no doubt there is a somewhat 

 ill-defined term of more or less spottiness, called the sun-spot period. If we 

 cannot as yet certainly connect it with radiations of additional heat or of light, we 

 can certainly trace its concordance with the varying intensities of the earth- 

 currents of electrical force. In my paper for our semi-centennial memorial 

 volume,* I brought down to that date my own studies on the subject, and to 

 avoid repetition, 1 refer thereto, especially as that was the first publication of my 

 discovery tbat the solar disturbances which cause sun-spots and our magnetic 

 storms aud auror^e al.so cause simultaneous excitation in the tails of comets and in 

 the condition of other planets. There has been no doubt since the publication of 

 Professor Loomis' papers in the American Journal of Science, many years ago, that 

 the curve of magnetic excitement followed very closely that of sun-spottiuess, and 

 the curves which prove their similarity have been brouglit down to the present 

 date by Mr. W. Ellis, F.E.A.S., attached to the Greenwich observatory. Shortly 

 after the date of my paper just referred to I made a curve from the differences 

 between the observed brightness of Encke's comet at its many apparitions and the 

 brightness it should have attained if distance from the earth aud sun had been the 

 only factors to be considered. That investigation, published in a Presidential 

 address to the Toronto Astronomical Society, showed that the excitation of that 

 comet has always corresponded in a most remarkable waj' to the magnetic 

 excitation of the earth, and therefore to the condition of the sun.f 



We have, however, been passing through a period of minimum solar 

 excitation, and I have on that account been giving less attention to phenomena 

 expected at active periods than to those which can be studied within walls and 

 ceilings, aud I have nothing new to say on that sul)ject.j; I find, however, that I 

 have not yet communicated to the Institute my demonstration that antarctic 

 aurorie are synchronous with auror;e boreales. This I was able to prove from the 

 observations of that painstaking and thorough meteorologist Henryk Arctowski, 

 now of Liege, who was with Commander de Gerlache on the Behjica during her 

 antarctic sojourn. His table of auronc seen in Belyica Straits, far to the south of 

 Cape Horn, answers precisely to the table made from Canadian and Washington 



* Transactions. Canadian Institute, i8i)8, 1899. p. 345. 



t Transactions, .Astronomical Society of Toronto, 189S. 



t Since the reading^ of this paper, the author has found reasons for believing that the zodiacal light also 

 brightens during magnetic disturbances. 



