Sept. 21, 1883.] 



♦ KNOWLEDGE ♦ 



189 



ill acquainted with the tastes of British readers ; unless it 

 is to be held that beneath a veneer of culture we have 

 exceedinjily coarse and savage tastes. Are we to suppose 

 that in cock-fighting, bull-baiting, public prize fights, and 

 other noble " sports " with which a " sentimental law- 

 making " has interfered our innate savagery found a 

 wholesome vent, and that now, wanting these, our people 

 require to be supplied with " gallows news " to satisfy their 

 hankering for what is savage and brutal ? I fancy the 

 leaders of public opinion (Heaven save the mark) might 

 safely have credited us with better taste. 



It may be urged that as we must have executioners so 

 long as capital punishment is in vogue, the holder of the 

 office ought not to be held in contempt, or regarded as 

 necessarily a cruel and brutal wretch. There is, however, 

 no iimst in the case. In America for the last half century 

 there have been no " common hangmen " though capital 

 punishment is still awarded and occasionally inflicted. On 

 the Continent where there are executioners, their identity 

 is concealed. No one in Great Britain was ever driven by 

 want to take the office. The letters published so cheerfully 

 in the public journals may at least serve a useful purpose 

 in showing what manner of men hangmen are, — though 

 this might have been guessed without so ghastly and 

 degrading an exhibition. 



As to the propriety of capital punishment, nothing need 

 here be said. Taking the scientific view of the matter it 

 may be noticed that Nature inflicts capital punishment 

 relentlessly — if somewhat blindly — for less offences than 

 those for which the law assigns the penalty of death. If 

 there were no law for eliminating murderers from our 

 midst they would be removed ere long without law ; and 

 systematic elimination is better than irregular removal. 

 But in these days a more seemly system of capital punish- 

 ment ought to be adopted. 



Ciiitonal (Sosfsiip. 



A CORRESPONDENT is exercised in his mind because at a 

 recent meeting of the Astronomical Society certain doubts 

 were raised respecting a point in the Lunar Theory. He 

 tells me tliat a certain Mr. W. H. Phillips has devised " a 

 new theory of a serpentine course of the moon " to which 

 I ought, it seems, to have long since alluded. Mr. Phillips 

 " says plainly," writes my correspondent, " that your theory 

 and all astronomers an: irrmvj, and that the Royal Astro- 

 nomical Society had generously [acknowledged his new 

 discovery " — " so you see," he adds, referring to a former 

 communication, "I am not mistaken in what he says 

 about the Royal Astronomical Society owning to their 

 being wrong in this matter of a Lunar Theory." 

 This is not the first time that a discussion in 

 the Astronomical Society about some matter far beyond 

 the range of the general student, has been mistaken for 

 an expression of doubt about an elementary matter. I 

 remember that the late Mr. Reddie, paradoxist and founder 

 of the Victoria Institute, was convinced that the Astro- 

 nomical Society and the Astronomer Royal in particular, 

 were coming round to his views, becausi; Sir George Airy 

 showed that the theory of the sun's proper motion in space 

 was as yet by no means complete. Mr. Reddie had not 

 the least idea what "the sun's propi^r motion in space" 

 might mean ; but he had ventilated some wild ideas about 

 elementary astronomical matters and especially about the 

 sun's fixity of position, so he immediately jumped at the 

 conclusion that Sir (icorge Airy had heard of these notions 

 and was speaking of tluun. Now as a matter of fact Mr. 



Reddie's letters had long since found a place on the shelf 

 which Sir George Airy had cruelly labelled, 



"MY LUNATIC ASYLUM FOR LUNATICS." 



It ought not to be necessary for me to explain that the 

 douljts raised recently by Mr. Stone respecting the Lunar 

 Acceleration have nothing whatever to do with the ordi- 

 nary account given by astronomers respecting the moon's 

 motion round the earth and (with her) round the sun. 

 There never has been any doubt about this point since the 

 Copernican theory was established, — and there never can 

 be (that is, among astronomers). When astronomers speak 

 of the Lunar Theory they do not refer to so elementary a 

 matter as this ; but to the mathematical analysis of those 

 multitudinous perturbations which the moon's movements 

 undergo, by which she is now swayed a little on this side 

 now a little on that side, now a little above anon a little 

 below, the course she would pursue if undisturbed in her 

 combined elliptical paths around earth and sun. This 

 course would differ little from an ellipse around the sun 

 at one focus ; for as Sir George Airy neatly put it (in a 

 letter to Mr. Reddie) the moon may be regarded as a planet 

 travelling around the sun but largely perturbed by the 

 attractions of a neighbouring planet, the earth. The 

 analysis of the other perturbations and of the constant 

 fluctuations in the elements of the moon's apparent orbit 

 round the earth, constitutes what is called the Lunar 

 Theory, a subject which none but advanced mathematicians 

 can hope thoroughly to grapple with, far less to deal with 

 so as to advance our knowledge respecting it. The Dif- 

 ferential and Integral Calculus is the A B C of the subject 

 and of all kindred subjects. As we want to be a good 

 deal Ijeyond the A B to read profitably, so must the 

 mathematician be far beyond his first acquaintance with 

 the " Dif-Cal " to follow the complex reasonings involved 

 in the Lunar Theory. 



P.\RTS of the Lunar Theory remain still to be more fully 

 explored than as yet they have been. Among these must 

 be mentioned the Lunar Acceleration, that slight but 

 measurable hastening of the moon in her course, by which 

 she would not gain her whole apparent diameter in many 

 centuries. It was supposed at the beginning of the present 

 century that Laplace had explained this phenomenon fully, 

 by his masterly analysis of the efiect due to the gradual 

 diminution in the eccentricity of the earth's orbit. But 

 recently Professor Adams showed that when the analysis 

 was carried somewhat farther half the acceleration remained 

 still unaccounted for. After a long inquiry Adams' con- 

 clusions seemed established, and Delaunay suggested that 

 the part of the acceleration unaccounted for might be 

 apparent only, the real change being a constant but slow 

 retardation of the earth's rotation ; and he pointed to the 

 tidal wave as capable of retarding the earth's rotation, 

 though whether in suflicient degree to account for the 

 estimated change, he could not say. And now further 

 inquiry by Mr. Stone, Radcliffe Observer, indicates the 

 probability that with further and deeper analysis the 

 Lunar Theory may be able to account for the whole 

 acceleration after all, without our having to assume any 

 measurable retardation of the eartli's rotation. Yet retar- 

 dation of terrestrial rotation is doubtless taking place all 

 the time. 



The Delaunay mentioned in the preceding paragraph 

 must not be confounded with the Delaunay wlio has 

 ventilated absurd theories about the influence of tlie 



