Mav, 1901.1 



KNOWLEDGE. 



iU'J 



appear to our eyes as dark spots. In that case these 

 spots would ill uo way send forth any extra quantity 

 of heat, on the contrary, they would diminish the heat- 

 giving surface of the photosphere. But according to 

 all statistics this by no means agrees with our obser- 

 vations. 



Now I saw in the November number of Knowledge 

 for 1900. p. 254, that Baron Kaulbais had brought forth 

 a new hypothesis on the nature of solar spots. The 

 Baron indicates that as the suns temperature in all 

 probability rises the deeper one descends. " the lower 

 layers, which we see through the openings of the spots, 

 must be much liotter than the photosphere, and as such 

 their immense temperature produces vibrations of the 

 ether of so great a rapidity, and such minuteness of wave 

 length, that they are out of range of sensibility of oiu' 

 optic nerves, and therefore appear black." If this be the 

 case, it gives a simple explanation of the rise and fall 

 of the temperatiu'e of our seasons, in accordance with the 

 sunspot cycle. At a maximum the large amount of spots 

 would send forth an excess of heat, and at a miniiiuim 

 the suns temperature would be normal. 



Of coiu'se our temperatxire is subject to manifold 

 terrestrial disturbances, wherefore no absolute regularity 

 can be expected to be attained in evidence of a close 

 connection between the sunspot cycle and our waves of 

 heat and cold, but still the above statements seem to 

 afford some degiec of presumption as to the likelihood 

 of such a connection. Percy Quensel, t.f.k. 



Upsala, Sweden. 



[Mr. Quensel states that he has " been struck with 

 the fact that our temperatui-e is surprisingly dependent 

 on the number of sunspots." It is much to be desired 

 that Mr. Quensel should give the actual figures on which 

 he bases this statement. Right or wrong, it is not a 

 statement that can be accepted on anyone's ipse dixit, 

 but we do need most sorely the fullest and fairest possible 

 comparison of temperature records with the observed 

 sunspot curve. It must be borne in mind that if the 

 spots radiated absolutely no heat whatsoever yet the 

 change from the maximum to minimum would hardly 

 mean a change of one-tenth per cent, in the solar radia- 

 tion. Now we know that the radiation from a spot is 

 very considerable. The radiation from the faculas — • 

 most numerous when spots are most numerous — is pro- 

 bably in excess of that from the photosphere. We may 

 take it then that the extreme variation from dead 

 minimum to most active maximum in the total radiation 

 of the sun is not likely to exceed one part in ten thou- 

 sand. One would scarcely expect that so small a change 

 would produce a very, marked result upon our tempera- 

 ture curves. If Mr. Quensel has a clear case of such 

 connection, we should certainly be glad to see it. 



E. Walter Maunder.] 



THE NEBULAK HYPOTHESIS. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs. — Mr. Walter Mauuder's observations in the April 

 number of Knowledge are certainly not in accordance 

 with the theory propounded by Laplace. I have ahvays 

 been given to understand that Neptune, if that body 

 really determines the boundary of the solar system, was 

 the first planet to be detached from the parent mass 

 which was then (.supjiosed to Ijc) in a rapid motion of 

 rot.ation about a central axis. If this state of tbiu''s 



represents the true facts, then Mercury is the younfi;est of 

 the planets, and not the oldest, as Mr. .Maunder seems to 

 sugijest. Geo. McKenzie Knight. 



7, Sydenham Terrace, Louth, l,incs. 



TO the editors of knowledge. 

 Sirs, — Perhaps I may be allowed to refer your corre- 

 spondent Mr. Christopher to Trowbridge's ex|ilanation of 

 the anomalous rotation of Uranus and Neptune, as given 

 on jip. .570 and 571 of the new edition of Professor Young's 

 " General Astronomy," as affording to my mind a more 

 simple and rational explanation of the difficulty than that 

 furnished by Faye's more involved one. 



WiLI.lA.M NuliLE. 



Forest Lodge, Maresfield, Uclctield. 



[It may be pointed out that Mr. Maunder, who has 

 prifceeded to Mauritius to observe the coniing solar 

 eclipse, simply ijuoted Faye's niodificatiou of the nebular 

 h\ jiothesis ah a possible way of explaining some of the 

 facts which have come to light since the time of Laplace, 

 and is in no way responsible for the suggestion that the 

 interior planets are the oldest, as Mr. Knight's letter seems 

 to imjily. On the contrary, it was remarked that there 

 were very considerable difficulties attaching to Faye's 

 form of the theory. 



The explanation to which Captain Noble draws atten- 

 tion will also be found in the first edition of Young's 

 "General Astronomy." pp. .518, .519. The substance of 

 it is that when a ring has been detached and concentrated 

 into a single mass, the direction of axial rotation will 

 depend upon the original distribution of matter within 

 the ring ; if of uniform density, the rotation would be 

 retrograde, but if it were most dense near the inner edge, 

 the rotation would be direct. Prof. Young goes on to 

 say : " The fact that the satellites of Uranus and Neptune 

 revolve backwards is not, therefore, at all a bar to the 

 acceptance of the nebular hypothesis, as sometimes 

 represented." — Eds.] 



— ►.*-* — 



CONSTELLATION STUDIES. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — I have been very much interested in Mr. E. 

 Walter Maunders " Constellation Studies " in your 

 valuable paper, and would like to ask two or three 

 questions, trusting to receive a reply through your columns. 



In the February number, Mr. Maunder, writing of the 

 Coustellation Leo, says that "Gamma, Zeta and Epsilon 

 arc all interesting as opera-glass objects from the com- 

 panions which a slight optical assistance brings into view." 

 The Rev. T. W. Webb, in his list of doulile stars, gives 

 the distance of the comjjoiient stars of Gamma Leonis as 

 only 25" apart. Would an opera-glass sjilit this star'? 



Oil looking at Captain Smythe's " Bedford Catalogue " 

 1 find the two stars of Epsihjii Leonis are only 1"9" apart. 

 Surely no opera-glass could divide these ? 



The smaller of the component stars of Epsilon Leonis is 

 of the loth magnitude only. Could this be seen with an 

 opera-glass, even if the distance from the larger star were 

 greater ? Would not the light be much too dim ? 



In the March number Mr. Maunder says that " Zeta 

 Corvi, the faint star midway between Epsilon ami Beta 

 (Corvi J, shows with the opera-glass as a very interesting 

 double" Now the smaller star of this pair is ISS 

 magnitude. I should like Mr. .Maunder to say nhether 

 it would be possible to see a 138 magnitude star with an 

 opera-glass, whether indeed it would not be a difficult 

 object for a small telescope r Ernest L. Bkii.isy. 



West Biidgford, Ni.lU 



