August 1, 1888.] 



♦ KNO^VLEDGE ♦ 



235 



explanations which are perfectly correct, heing, La fact, only 

 altered in a few words from an explanation given by 

 Newcomb or Airy, or others who understood what they 

 were explaining. Again, many of the illustrations are 

 excellent, being, in fact, those provided to accompany correct 

 explanations in books worth reading. But the trouble is 

 that the re:ider, who is also a learner, can never be quite 

 sure whether what he is reading is a correct and well- 

 iUustrated explanation borrowed from an able astronomer, 

 or sheer nonsense which he should forget quam celerriine. 



It is a duty which we owe to the honest student of astro- 

 nomy to say so much as may keep him from wasting his 

 time over this most remarkable production. We have not 

 time to indicate all the passages which are incorrect or 

 absurd ; neither would it be fair to those writers whose 

 correct statements have bsen repeated, to show how by 

 eliminating such and such portions (all Mr. Lockyer's 

 original work, we suspect) their good explanations would 

 remain (little impaired by verbal changes) with their excel- 

 lent accompanying illustrations. 



The fairest course seems to be to give a few samples, 

 takea absolutely unchanged from ISlr. Lockyer's book 

 (though many will find it hard to believe as much), to show 

 that we have not exaggerated either the condescending tone 

 of the work, or the utter inanity of the original (indeed, 

 highly original) matter. 



In the following passage, Mr. Lockyer opens his explana- 

 tion of the apparent motion of the star-sphere : — 



Suppose that ia the centre of a lecture-theatre a Utile globe were 

 hung to represent the earth, the walls oE the theatre and the people 

 in it representing the heavens surrounding the earth. In such a 

 case it is clear that the appearances presented would be the same 

 whether the heavens moved round the ear;h, or the earth itself 

 were endowed with motion. Let us, without making the assertion, 

 assume that the earth does move. It is perfectly obvious, since the 

 apparent motions of the heavens are so regular, that it that be so, 

 she must move with wonderful constancy and regularity ; she does 

 not first move in one direction and at one inclination, and then at 

 another ; that would be very serious. 



If she rotates she must rotate round some imaginary line called 

 an axis. This introduces an important consideration, because, 

 whether the earth itself rotates on an axis, or the heavens move 

 round the earth — and in the latter case the heavens must also move 

 round an axis — in either case the motion must be an equable one, 

 so that if the matter is thus limited to a constant axial rotaiion, or 

 a constant revolution as it would be called in the case of the stars, 

 several things will happen. 



And so the explanation maunders on. 



Here is another exquisite bit of " explanation " : — 



If we assume the earth to rotate, we mast carefully consider the 

 varj'ing conditions which are brought about by the different 

 positions of an inhabitant of the earth under those circumstances. 

 For instance, take the case of a man at the equator : he looks at 

 things from an equatorial point of view, and in the rotation of the 

 earth he plunges straight up and straight down. 



Having in the fashion thus illustrated " explained " the 

 apparent daOy motion of the stars, Mr. Lockyer proceeds 

 to explain their apparent diurnal motion. Here is the 

 " explanation " : — 



The same difficulty that was met with before is again encountered 

 here — Is this movement of the sun among the stars a real or an 

 apparent one ? It is a question, however, which has been long since 

 answered ; and it can be very definitely stated, not only that the 

 earth rotates on its axis in a period of twenty-four sidereal hours, 

 but that it moves or revolves round the sun in a period which we 

 call a year, and that it is this real movement which causes the ap- 

 parent one of the sun among the stars. Let the reader take a top 

 and spin it. Perhaps the top has a movement of progression as well 

 as a movement of rotation, and it is in that way quite easy to see 

 that the earth may rotate on its axis and revolve about the sun at 

 one and the same time. And with a top of special construction its 

 axis of rotation might be inclined so that its plane of rotation 

 ceased to coincide with the plane of its motion of progression ; still 



the two mavements would go on, and in whatever position the top 

 might be placed, its axis might be made to remain practically 

 parallel to itself during its movements. We may now, then [oh, 

 this OTKrf be a joke !], make the following statements: — T/ie earth 

 7'crali'es round the sun, and t/irougliout the revolution the axis of 

 rotation remains practicallij parallel to itself. With regard to the 

 latter part of this statement, it may be added that if this were not 

 so — if the axis of the earth were subject to perpetual change of 

 direction — the declinations of the stars would also be subject to 

 constant change. 



Finally, here is a passage from Mr. Lockyer's explanation 

 of the aberration of the fixed stars : — 



In the case of the majority of the stars what we get is an ellipse, 



and in an ellipse we have certain differences which have to be taken 

 into account, the last difference of all being that an intiniteiy 

 elongated ellipse is a straight line, and it is found that from one 

 particular point of the heavens where, in consequence of this 

 aberrational motion, the orbits of the stars round their mean places 

 are almost circular, we at last get to a point where the motion is 

 simply an oscillation of the star backwards and forwards to and 

 from its mean place : we are dealing, in fact, with that projection 

 of the ellipse which takes the form of a straight line. Wtien we 

 deal with an ellipse we no longer talk of the radius, but of the 

 semi-axis major, which is half the greatest length. The angle of 

 aberration of which I have spoken only amounts to 20"'492, but 

 though small, it is quite enough to prove that the earth does re- 

 volve, and that consequently the sun is the centre of the system to 

 which the earthbelongs.whileit further tells usthat the movement of 

 the earth is slow compared with that of light. 



Ltickily no reader is likely to suppose he is really getting 

 any explanations in such passages as these. 



By Eichard A. Proctor. 



IIessrs. Maunder & Knobel desire to have it explained 

 that the unnamed " Professor " referred to in " Gossip " for 

 April did not appeal to them, as I had surmised and naturally 

 (almost necessarily) beheved — see p. 138 — to announce 

 (in a magazine which I was certain not to see and almost 

 certain not to hear of) that I had not actively assisted his 

 election to the Foreign Associateship of the Royal Astro- 

 nomical Society. They did this thing of their own accord, 

 not at the " Professor's " instigation at all. I willingly 

 accept and publish their contradiction of my most natural 

 mistake. They agree in speaking of this mistake as 

 injurious; but without explaining how or why it was 

 injurious, or whom it could possibly injure. It could not 

 injure their protege, he being past that; and though cer- 

 tainly it ought not to be pleasing to them to be supposed to 

 be in correspondence with him, they had published more 

 than that about themselves in the very letters on which I 

 commented. 



* * * 



TiiE case was simply this — Messrs. Knobel & Maunder 

 chose on partial information, amazingly misunderstood, to 

 interfere in a matter in which they had no sort of concern, 

 undertaking to contradict what I had not said and what a 

 moment's reflection should assure any honest mind that I 

 could not have intended to say. (Mr. Maimder admits in 

 a letter from which, though marked " private," I am entitled 

 in self-defence so f;xr to quote, that when the complete cor- 

 respondence, of which he and Mr. Knobel had seen only 

 part, was before him, the impression he had formed of my 

 meaning was "proved not to be the one I intended to con- 

 vey " ; and I maintain that even with the one letter he had 

 seen mv meaning should have been as clear as day to him 

 and to Mr. Knobel.) For reasons best known to them- 

 selves they selected as a suitable place for the attempted 

 injury to me a magazine which I never see, as they can 



