I50 



NATURE 



\June 1 6, 1 88 1 



commercial, left Beilul last April to explore the source of the 

 Gualima. Four days distance from that town they were attacked 

 and slain by the natives. Signor Giulietti was well known for 

 the difficult journey he accomplished from Zeila Hazar. He 

 was asked by the Geographical Society to explore the interior 

 of the west coast of the Red Sea. At (irst a journey to Lake 

 Aussa was contemplated, but obstacles arising, the plan was 

 changed for an expedition into the Assab Gallas country. 



At the meeting of the Geographical Society on Monday last 

 Capt. W. J. Gill, R.E., read some extracts from a long account 

 of his explorations in Western Szechuen, which has lately been 

 sent home by Mr. E. Colborne Baber, now Chinese Secretary of 

 H.M. Legation at Peking. The extracts chosen dealt chiefly 

 with the amusing side of Mr. Baber's journey, but the paper, 

 nevertheless, contains abundance of solid information respecting 

 the extreme west of China, and, as Lord Aberdare stated in his 

 anniversary address, is considered by competent judges to be a 

 noteworthy contribution to our kuo^\'ledge of Asiatic geography. 

 The mo->t valuable part of the extracts read is probably that 

 respecting the almost unknown Lolo country, in the neighbour- 

 hood of Ning-yiian-fu. Mr. Baber sent home copies of some 

 pages of a Lolo manuscript, no specimen of which, we believe, 

 has ever been seen in Europe before. These have been sub- 

 mitted to the well-known scholar, M. Terrien de la Couperie, 

 who gave the meeting a brief account of the results of his exa- 

 mination of them. Mr. Baber's paper will be published by the 

 Society, together with the valuable cartographical matter which 

 accompanied it. 



M. AND Madame Ujfalvy were to leave Simla for Kashmir, 

 viA Kangra, on June 6. From Kashmir they hope to penetrate 

 into Thibet and Central Asia. 



The death is announced of Mr. Andrew Wilson, author of a 

 well-known book of travel in the Himalayas, "The Abode of 

 Snow." 



SOLAR PHYSICS— CONNEXION BETWEEN 



SOLAR AND TERRESTRIAL PHENOMENA ' 



IL 



T N my last Lecture I alluded to the complicated periodicity 

 ■'■ which sun-spots exhibit. It is right here to quote the 

 remark of Prof. Stokes, that until we have applied to solir 

 phenomena a sufficiently rigid analysis we are not certain that 

 this apparent periodicity will bear all the marks of a true 

 periodicity. It cannot however be denied that solar phe- 

 nomena are roughly periodical, and this apparent periodicity 

 has influenced observers in their attempts to search for a 

 cause. There have been two schools of speculators in this 

 interesting region, 'consisting of those who imagine a cause 

 within the sun, and of those who imagine one without. The 

 former may be right, but apparently they cannot advance our 

 knowledge much. We know very little of the interior of the 

 sun, and no one has yet ventured on any hypjthesis regarding 

 the modus operandi by which these strangely complicated and 

 roughly periodical surface phenomena may lie supposed to be 

 produced by the internal action of the snn itself. 



Those who maintain the hypothesis of an internal cause are 

 apparently driven to it by the a priori unlikelihood of any cause 

 operating from without. No doubt we have around the sun 

 bodies, the m-jtions of which are strictly periodical, such as 

 planets, comets, and meteors, but they are relatively so small and 

 so distant, that it seems difficult to regard them as capable of 

 producing such vast phenomena as sun-spots. 



There is however this difierence between the two hypotheses 

 — those who assert internal action cannot convert their views 

 into a working hypothesis. On the other hand, those who look 

 to external sources can take the most prominent planets, for 

 instance, and endeavour to ascertain whether as a matter of fact 

 the behaviour of the sun with regard to spots is apparently 

 influenced by the relative positions of these. Attempts of this 

 nature have been made by Wolf, Fritz, Loomis, Messrs. De La 

 Rue, Stewart, and Loewy, and others. These attempts have 

 been of two kinds. In the first place observers have tried 

 whether there appear to be solar periods exactly coinciding with 

 certain well-known planetary periods. By this means the 



' Lecture in the Course on Solar Pliysics at South Keniington ; delivered 

 by Prof. Balfour Stewart, F.R.S., April 27. Continued from p. 117. 



following results have been obtained by the Kew observers 

 (Messrs. De La Rue, Stewart, and Loewy) : — 



(1) An apparent maximum and minimum of spot energy 

 approximately corresponding in time to the perihelion and 

 aphelion of Mercury. 



(2) An apparent maximum and minimum of spot energy 

 approximately corresponding in time to the conjunction and 

 opposition of Mercury and Jupiter. 



(3) An apparent maximum and minimum of spot energy 

 approximately corresponding m time to the conjunction and 

 opposition of Venus and Jupiter. 



(4) An apparent maximum and minimum of spot energy 

 approximately corresponding in time to the conjunction and 

 opposition of Venus and Mercury. 



Mr. De La Rue and his colleagues make the following remarks 

 upon these results : — 



" There appears to be a certain amount of likeness between 

 the march of the numbers in the four periods which we have 

 investigated, but we desire to record this rather as a result 

 brought out by a certain specified method of treating the 

 material at our disposal, than as a fact from which we are at 

 present prepared to draw conclusions. As the investigation of 

 these and similar phenomena proceeds it may be hoped 

 that much light will be thrown upon the causes of sun-spot 

 periodicity." 



I may here mention that within the last month 1 have, in 

 conjunction with Mr. Dodgson, applied a method of detecting 

 unknown inequalities with the view of seeing whether there are 

 any indications of an unknown inequality in sun-spots having a 

 period near that of Mercury, and I lind there are indications of 

 sucli an inequality having a period which does not differ from 

 that of Mercury by more than about three-hundred ths of a day. 

 Besides the four periods above mentioned the Kew observers 

 have, they think, detected evidence of a periodicity in the 

 behaviour of spots with regard to increase or diminution de- 

 pending apparently on the positions of the two nearer planets. 

 Mercury and Venu^. The law appears to be, that as a portion 

 of the sun's surface is carried by rotation nearer to one of these 

 two influential planets, there is a tendency for spots to become 

 less and disappear, while on the other hand when it is carried 

 away from the neighbourhood of one of these planets there is a 

 tendency for spots to break out and increase. 



The Kew oljservers regard this latter species of evidence as 

 being well worthy of a more exhaustive discussion when the 

 sun-spot records are more complete. I have already mentioned 

 that the chief difficulty in attributing solar outbreaks to con- 

 figurations of the planets is the comparative smalluess and great 

 distance of these bodies, so that when we reflect on the enormous 

 amount of energy displayed in a sun-spot we cannot but have 

 great difficulty in supposing that such vast phenomena can be 

 caused by a planet like Venus, for instance, that is never as near 

 to the sun as she is to the earth. But this difficulty depends 

 very much on what we mean by the word "cause." If we 

 mean that the planets cause sun-spots in the way in which the 

 blow of a cannon-ball or the explosion of a shell causes a rent 

 in a fortification, the hypothesis is certainly absurd. But if we 

 only mean that the planets act the part of the man who pulls 

 the trigger of the gun, the hypothesis may be unproved, but it is 

 no longer absurd. For we have reason to believe that there 

 may be great delicacy of construction in the sun's atmosphere, 

 in virtue of which a small cause of this kind may produce a 

 very great effect. 



We may therefore believe it possible that planets may act 

 in this way on the sun — the energy displayed in a spot being 

 however not derived from the planets, but from the sun itself, 

 just as the energy of a cannon-ball is not derived from the man 

 who pulls the trigger, but from the explosion in the gun. 



All this is chiefly historical, and it leads to a very interesting 

 query. If there is such an action of a planet on the sun, must 

 not this have a reaction ? If the earth influences the sun, must 

 not the sun simultaneously influence the earth ? Perhaps so ; 

 nevertheless it is not an inflnence of this kind which I shall 

 now bring before you. The sun is periodically stirred up — no 

 matter how — and being stirred up there is an increase in the 

 light and heat which are radiated to the earth. This affects the 

 meteorology of the earth, and also its magnetism, after a method 

 which, if we do not fully understand it now, we may ultimately 

 expect to comprehend. It is this kind of influence, and not 

 an occult action, of which I shall now bring the evidence 

 before you 



