No\-BMBER 1, 1900.] 



KNOWLEDGE. 



253 



I cannot help recurring to the foot-note which Mr. 

 Maunder appended to Mr. East's article ou artificial 

 suuspot.s in the December (1S97) issue of Knowledge. 

 Undoubt<>dly instructive as Mr. East's experiments are, 

 he allows himself to be carried too far in drawing con- 

 clusions and pointing to analogies between solar 

 " phenomena and a peaceful domestic experiment. It 

 seems to me nothing short of extraordinary on the 

 strength of this latter to even doubt the convertibility 

 of maximum sun-spoltedness and maximum solar 

 activity. To be thus, after many years of independent 

 study with telescope and spectroscope, confronted with 

 the proposition that maximum spottedness is syn- 

 chronous with solar quiescence is upsetting accepted 

 theories with a vengeance. 



I have no desire to be flippant, having the subject 

 too seriously at heart, but to come now, in the face of 

 all the information gained as to coincidence of spots, 

 prominences, faculse, aurora>, and magnetic storms, vivid 

 reversals of spectral lines and distortions, and upset all 

 this because of heating some stuff in a boiling pan, is 

 going too far. Certainly may we believe that solar 

 phenomena arc different tii their. known terrestrial con- 

 freres in their intensity only, but where are in Mr. East's 

 experiments the stujjendous potentials of temijeraturo, 

 pressure, chemical affinities, tremendous velocities, and 

 the host of incidental physical conditions of which we 

 have hardly a proper conception ? These solar conditions 

 possibly involving natural laws, which are for ever 

 hidden from human knowledge. But to touch directly 

 on the matter under discussion. 



I do not believe for one moment that the actual or 

 visual appearance of the photosphere influences spot 

 formation, but, if anything, that spots about to form 

 influence the appearance of the photosphere locally. 

 Mr. East mentions that compactness of the pliotospherio 

 material favours spot appearance, and yet again says, 

 that the solar poles will never show spots " for there the 

 photospheric matter will always be too closely packed. " 

 What are we to make out of such inconsistent argu- 

 ments? Incidentally I may mention that Mons. Jaussen 

 is more reserved as to a different construction of the 

 reticulation of the photosphere in the polar regions as 

 compared with that in the lower latitudes. He says 

 on page 113 of his excellent work : — 



" Nous n'avons pu, jusqu'ici, trouver de differences 

 appreciables entrc les regions qui, sur ces images, 

 environment le pole et celles des regions equatoriales. ' 



" II parait done, jusqu ici, que le phenoniene de la 

 granulation est un phenomene general a la surface de 

 la photosphere, ct qu'il nest pas en dependence imme- 

 diate avec celui des taches." 



No doubt, as Mr. East says, the photosphere is torn 

 and churned and dispersed, but by what? I venture 

 to say by spots, and all the other eruptive phenomena 

 connected with them, and that therefore the maximum 

 disturbance of the photosphere is reached practically 

 at the same time as the spot, faculse, and prominence 

 cycle reaches also its maximum. Certainly the sea may 

 be violently disturbed also after the stoi-m has passed, 

 but still it is not conceivable that the disturbance 

 reaches its maximum much after the storm is at its 

 climax. The passage from solar maximum activity to 

 minimum is a very jerky process, and the present 

 minimum is a strong case in point, inasmuch long after 

 maximum spot activity, that is, after the photosphere 

 is so unfavourable to spot formation, we have had spots 

 of extraordinary size and ditto prominences accompanied 



by auroral displays as late as September, 1898. In 

 short, to my lay mind, it is impossible to imagine that at 

 «. time of maximum solar activity I should for consecu- 

 tive days direct the telespectroscope towards the sun, 

 sec no spots and facula;, and find the edge of the disc 

 as smooth almost as on a turned flywheel. 



The argument Mr. East uses to supjiort liis view, 

 viz., the coincidence of the spot and prominence 

 maxima, is also open to objection. Mr. East/ argues that 

 " when the photosphere is diffuse, the solar flames will 

 have but little altitude, when compact all the force is 

 concentrated at the openings of the spots and vast jets 

 of flame are expelled." First let me .say that promi- 

 nences, as a inilc, do not issue out of the spot cavity, as this 

 sentence would lead the reader to assume. Furthermore, 

 according to this thesis, one must expect to sec the tallest 

 prominences in the polar regions, as there the jslioto- 

 sphere is closely packed, as he states elsewhere. My 

 own observations confirm what Prof. Young states, 

 namely, that eruptive prominences appear in the imme- 

 diate neighbourhood of spots and never near the poles. 



When I look over Mr. East's article in general, I 

 must confess I am unable to sec what he is desirous 

 to establish or driving at, and his conclusions drawn 

 from his experiments are far from convincing. Again, 

 Mr. East's conception of the origin of prominences, 

 which he illustrates by another experiment, puts a 

 limit to the appearance of these eruptions which is out 

 of all agreement with actual observation. His pro- 

 minences must all be of one '' style " and almost 

 tediously alike, and only different in height at various 

 periods. 



There is one point in Mr. East's studies the value of 

 which I set far above his comparisons and conclusions, 

 and that is that he keeps along a line which centres in 

 the assumption that the causes of solar evolution are to be 

 found on the sun itself. 



As to a satisfactory explanation of the periodicity of 

 spots, etc., no satisfactory solution has come up yet, nor, 

 I venture to say, ever will, making respectfully all allow- 

 ance for future progress of science. We have had the 

 influence of the planets or the periodic return of a 

 large aggregation of meteorites close to the sun as special 

 favourites, but all these propositions carry with them 

 a great deal of doubt and little conviction. As we see 

 the periodicity to be variable to an average extent of 

 two years for successive minima and maxima, it is only 

 likely that these two theoiies will break sadly down. 

 Since to my mind the cause of the cycle is to be found 

 on the sun itself, and is to my conviction contained in the 

 solar contraction and the contending forces set up by it, 

 it is not difficult for me to conceive that successive 

 pulsations cannot be at exact intervals of time, and, as 

 Mr. East says, each successive disturbance is influenced 

 by the gi'eater or lesser intensity of the preceding one. 

 The very magnitude of the sun's proportions seems to 

 imply a rhythm of pulsation appropriate, and if 11.11 

 years have been found to represent the average of these 

 periods, it is quite reasonable, if perhaps not very scien- 

 tific, to simply accept this fact. We never seem to 

 trouble our heads much about finding out how it is that 

 the earth takes about 365 days for completing her orbit, 

 or why the sun rotates once in about 2.5 days, and 

 similar unsolvabic problems. 



Albert Alfred Buss, 



9, Grosvcnor Square, Ashton-on-Mersey, 



[May I point out that there is no inconsistency of 

 argument as to the absence of spots at the solar poles. 



