208 



KNOWLEDGE 



[September 1, 1894. 



THE PERIODICITY OP THE SOLAR SPOTS, AND ITS 

 CAUSE. 



To the Editor of Knowledge. 



Sir, — In his exceedingly interesting article, "A Pro- 

 longed Sunspot Minimum," in the August number of 

 Knowledge, Mr. Maunder mentions that the cause of the 

 periodicity of the solar spots has been ascribed to the 

 periodical returns of the planet Jupiter to the perihelion 

 of its orbit, but significantly adds that if this were the 

 true cause, " since that return is regular, pmictual, and 

 unfailing, so ought its effect to be, and it should be as im- 

 possible for the sun to intermit two or three of its cycles as 

 for Jupiter to wander from his orbit." To me the theorv 

 in question never had much to recommend it ; not only is 

 the eccentricity of Jupiter's orbit very small — less than 

 that of Saturn, and considerably less than that of Mars — 

 but his period (11-9 years) is much longer than that of the 

 average period of the solar spots. The facts about the 

 latter which are adduced by Mr. Maunder are surely 

 sufficient to negative any connection between the 

 periodicity of the spots and the regularity which 

 characterizes planetary motions, disturbed only by per- 

 turbations which cannot affect such a question as this. 



Some little time ago, I suggested in TJie Obsen-aiori) that 

 the recurring maxima and minima of solar spots might be 

 due to a swarm of meteoric bodies which move in an 

 eccentric orbit, and pass, when in perihelion, near the 

 outer envelope of the sun. Although the period suggested 

 by Schwabe for the solar spots was 10'4 years, it is now 

 well understood that the true average period amounts to 

 11-1 years. Now a body or bodies revolving round the 

 sun with this period would have a mean distance from 

 him of ■1-98 in terms of the earth's mean distance ; 

 and if the perihelion distance were small, the aphelion 

 would not differ much from that of Satiirn. L'Astirinomie 

 did me the honour to refer to my suggestion, but pointed 

 out that the details of explanation and of the action of 

 the meteors were wanting. Now time may supply what is 

 certainly beyond my power at present ; but it seems to me 

 that if the theory be true, one remarkable detail in connec- 

 tion with it is suggested by this article of Mr. Maunder. 

 "The sequence," he justly remarks, " of maximum and mhii- 

 mum has been unfailing during the present century." He 

 then goes on to dwell on his main point, that not only 

 this cannot be affirmed of the phenomena during preceding 

 centuries, but the observations recorded, though not made 

 of course with Greenwich regularity and perseverance, are 

 abundantly sufficient to prove that the matter was then 

 far otherwise ; and particularly that during the fifty years 

 which elapsed from 1655, or thereabouts, to 1705, very 

 few solar spots were seen, or, as he puts it, " an extra- 

 ordinarily and immensely prolonged minimum " subsisted. 

 But what if regiilar maxima and minima had not then 

 begun to be, and the spots seen previously were of a more 

 sporadic kind ? Le Terrier thought that the Leonid 

 meteors were introduced into our system by the attraction 

 of Uranus about the second century after Christ. Perhaps 

 the swarm of meteors to which I suggested we owe the 

 present regular recurrence of the spots may have been 

 introduced by the attraction of Saturn in the early part 

 of the eighteenth century. 



Yours faithfully, 

 Blackheath, August 10th, 1894. W. T. Lynn. 



[I would refer Mr. Lynn to Prof. Eudolf Wolf's paper 

 on " Sunspot Maxima," published in the Memoirs of the 

 Royal Astronomical Society, Vol. XLtll. Unless he is pre- 

 pared to reject Prof. Wolf's laboriously collected evidence, 

 he must admit that there have been wide variations in the 



form of successive waves of the svinspot curve, even during 

 this century ; thus Wolf gives a sunspot maximum in 1804, 

 another in 1816, followed by another which was deferred 

 till 1830, while the next maximum period followed in 

 1836-7, giving intervals of twelve, fourteen and six and a 

 half years. Such tidal action as Mr. Lynn suggests would, 

 if caused by a single flight of disturbing bodies, necessarily 

 be regular. — A. C. Eanyard.] 



ANTARCTIC BIRDS. 



By WiLLiAii S. Bruce, Xnturalist to tlu Antarctic 

 Expedition, 1892-93. 



THE term " Antarctic regions " is vague, and it is 

 necessary to define to our readers the hmits of 

 this region about which we have such scanty 

 records. The Antarctic Ocean proper is that 

 portion of the great oceanic area of our globe 

 which lies within the Antarctic circle, or south of the 

 latitude of 66i° S. In dealing with the Antarctic, 

 however, few, if any, writers confine themselves to this 

 area. Many include regions as far north as Patagonia, 

 Falkland Islands, south of South Africa, south of Austraha, 

 and the south of New Zealand, while others vary their 

 limitations of the Antarctic by various locahties lying 

 between these northern and southern limits. In this 

 article it is proposed to call those birds Antarctic birds 

 which are to be found in higher southern latitudes than 

 the extreme limit of floating ice according to the most 

 recent research. The northern boundary of these regions 

 is somewhat irregular, but roughly may be said to extend 

 as far north as 40° S., i.e., a latitude corresponding to that 

 of Madrid and New York in the Northern Hemisphere. 

 This excludes Tristan d'Achuna, South Afi-ica, and 

 Australia — which lie north of 40° S. — Tasmania, New 

 Zealand and Auckland Islands, South America and the 

 Falkland Islands, and Kerguelen Island ; for although these 

 last-named are in latitudes south of 40° S., yet the ice 

 line rises southward in their respective longitudes. Three 

 exceptions are made to this boundary, viz., the Tristan 

 d'Achuna group, Kerguelen, and the Auckland Islands, 

 which have always been associated so intimately with 

 Antarctic exploration. In this way we exclude the great 

 continental masses, save Antarctica itself, but include 

 almost all those islands which most writers term Antarctic 

 islands. 



With few exceptions, the birds of the Antarctic are all 

 oceanic species, the penguins and the petrels being by far 

 the most important groups. Besides these, there are also 

 gulls, terns, and the remarkable sheathbills or paddies. 

 Let us first consider the penguins, which are perhaps the 

 most typical of aU Antarctic birds, although they may also 

 be found as far north as the Galapagos group of islands, 

 which lie almost upon the equator, off the west coast of 

 South America. 



A very interesting and graphic description of these 

 remarkable birds has been given by the late Prof. Moseley.* 

 Whilst the " Challenger " was in the vicinity of the 

 Tristan d'Achuna group, he says, " as we approached 

 the shore I was astonished at seeing a shoal of what 

 looked like extremely active, very small porpoises or 

 dolphins. I could not imagine what the things could be 

 unless they were indeed some most marvellously small 

 cetaceans ; they showed black above and white beneath, 

 and came along in a shoal of fifty or more from seawards 

 towards shore at a rapid pace, by a series of successive 



* " Xotes by a Naturalist on H.M.S. Challenger," by Moseley .- J. 

 Murray, London. 



