Oct., 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



237 



Sunspot VoLriaLtion in 

 Latitvide. 



By v.. Walter Maunder, F.R.A.S. 



In his letter, under the above title, in the August num- 

 ber of this journal Dr. Lockyer complains that I-ather 

 Cortie and myself have misunderstood, the meanint; of 

 the term " spot-activity track " which he has 

 originated. I think this complaint has no justification 

 in fact. Certainly, for myself, I did not suppose that 

 he intended the term to apply to the proper motion of 

 any individual spot, but it is abundantly clear that he 

 did intend to intimate by it that the spots were 

 gathered together in certain districts or regions, 

 separated from each other by broad barren intervals, 

 and that these districts, rich in spots, moved continu- 

 ously downwards towards the equator ; so that the 

 entire " eleven-year period " was the summation of 

 three, four, or five separate and distinct shorter cycles 

 cf activity. Dr. Lockyer himself applies the term 

 " zone " to these districts ; he has drawn them in his 

 diagrams as distinct, widely separated, areas, each 

 one moving continuously towards the equator ; and his 

 descriptions of them perfectly accord with his dia- 

 grams. He writes : — 



" From sunspot minimum to minimum there are 

 three, but generally four distinct ' spot-activity 

 tracks,' or loci of movements of the centres of 

 action of spot disturbance." (Proc. R. S., Vol. 

 LX.XIIL, p. 147.) 

 Again : — 



" These ' spot-activity tracks ' have possibly a 

 terrestrial equivalent in the variations from year 

 to year of the positions of the ' Zugstrassen ' or 

 cyclone tracks of Kiippen, it having been found 

 that cyclones in general, which move in the 

 direction of the great mass of air carried by 

 primary currents, have a strong tendency to 

 pursue somewhat the same tracks according to 

 the place of origin." (Ibid, p. 147.) 

 Vet again : — 



" .Spoerer's Law of .Spot Zones is only annroxi- 

 mately true, and gives only a very general idea 

 of sunspot circulation. Spoerer's curves are the 

 integrated result of two, three, and sometimes 

 four ' spot-activity track ' curves, each of the 

 latter falling nearly continuously in latitude." 

 (Ibid, p. 152.) 

 Again, speaking at the Royal Astronomical Society, 

 on 1903, May 8, Dr. Lockyer said : — 



" The general idea about the spot zones is that 

 spots begin in a zone in high latitudes (about 

 + 30° to + 35°), and this zone gradually ap- 

 proaches the equator until the spots vanish 

 about latitude ± 5", the new cycle commencing 

 again in + 35". \ow a glance at this diagram* 

 shows that this is far from correct, because 

 sometimes there are two, and occasionally three 

 spot zones in existence in one hemisphere at r)nc 

 moment. Take the case of the year 1893, when 

 you have three zones. The curves of .Spoerer 

 are, therefore, very misleading, for by taking 

 the mean position of several spot zones you 

 arrive at a latitude in which spots may not exist 

 at all." (Observatory , 1903, June, p. 236.) 



•The diagram of my paper communicated to the Society at this 

 meeting, 1903, May 8 



It was because these descriptions answered to no- 

 thing on the sun that I communicated a " Note on the 

 Distribution of .Sunspots in 1 leliographic Latitude" 

 to the Royal Astronomical -Society at its last meeting. 

 I explained therein the nature of the mistake which 

 Dr. Lockyer had made with regard to the maxima on 

 w hich he based his paper, and that his method of join- 

 ing them up so as to show apparent fines of drift was 

 not only purely arbitrary, but was often against very 

 distinct and positive evidence. 



Is Dr. Lockyer 's statement that his " spol-aclivity 

 tracks " " are not tracks on the solar disc," and that 

 his paper, read before the Royal .Society in 1904, 

 I'ebruary 11, has been "misunderstood," intended as 

 a uillulrawal of these descriptions and detinitions of 

 " spot-activity tracks " which I have quoted — in fact, 

 of all the main body of his paper? If so, I think it 

 was a pity to publish in " Knowledge and .Scientiiic 

 News " a diagram to explain how he had been led to 

 take up a position which he now finds to be untenable. 

 Dr. Lockyer objects to the note on p. 159 in this 

 journal for July, and claims that I'^ather Cortie rather 

 corroborated than opposed his result. I do not so 

 read Father Cortie's paper. His words are : — 



" These facts, however, as to the persistence of 

 the disturbance in definite regions at some 

 epochs, and dearth of spots at others, do not 

 lend much countenance to the view of the varia- 

 tion in latitude being affected by a series of 

 ' spot-activity tracks.' " (Monthly Notices, Vol. 

 L.\IV., p. 766.) 

 The last two sentences in Dr. Lockyer's letter form 

 a claim wiiich ought not to have been made. He says : 

 " I pointed out, as one of the main results of my 

 investigation, that outbursts of spots in high lati- 

 tudes are not restricted simply to the epochs at 

 or about a sunspot minimum, but occur even up 

 to the time of sunspot maximum." (" Know- 

 ledge & Scientific News," 1904, August, p. 182). 

 Dr. Lockyer's "investigation," so far as it relates 

 to the years 1874-1902, consisted solely in taking the 

 results of my p.iper, prepared by the desire of the 

 .\stronomer Royal for the Royal Astronomical Society, 

 1903, May 8, and adding the figures there given, in sets 

 of ten, of five, and of three. A computer of average 

 skill would do this easily in a couple of hours. But the 

 effect of this treatment would not be to bring out the 

 fact to which he alludes, but rather to obscure it. He 

 found the fact ready to his hand, explicitly set forth in 

 three-fold fashion in this paper of mine upon which he 

 was avowedly working. It was set forth in the dia- 

 gr.'ims, in the numerical tables, and in the brief pre- 

 liminary text. The latter ran thus : — 



" -Spots in a higher latitude than 33° were at all 

 times rare, and when seen were never large or 

 long-lived. Taking them as a class by them- 

 selves they were seen irregularly, appearing ;it 

 times which did not seem to bear any fixed rela- 

 tion to any one of the four chief stages of the 

 sunspot cycle — minimum, increase, maximum, 

 and decline. Omitting these spots in very high 

 latitudes— a term which would cover a zone 10'' 

 wide in each hemisphere, from 33° to 42°, for 

 no spots were observed in a latitude greater than 

 420 — the years of maximum, 1883 and 1893, 

 showed spots in practically every latitude be- 

 tween 30" north and 30° south, and they were 

 numerous from about 8" to 240 in both hemi- 

 spheres." (Monthly Notices, Vol. LXIII, 

 P- 4-S2-) 



