COMETS 



By F. W. HENKEL, B.A., F.R.A.S. 



These still mysterious bodies have always been of 

 the highest interest both to the astronomer and the 

 " man in the street," and though the progress of 

 science has robbed them of much of the terror their 



occur from day to day, and the extraordi nan- 

 behaviour of parts of their substance when nearest 

 the sun, seem to indicate the existence of matter in 

 a physical condition unlike anything of which we 

 have experience here, and from the want of such 

 information our knowledge of cometary physics is 

 necessarily defective. Thus, to the wonder and 

 terror formerly inspired by a comet has succeeded 

 the scientific wonder and curiosity at beholding the 

 behaviour of "matter" under almost unimaginable 

 conditions. 



In earl) 1 days, no doubt from the rarity and 

 unexpectedness of their appearance and the remark- 

 able nature of the appendages which many of them 

 possess, comets were regarded with fear and trembling 

 not only by the general public but also by the 

 learned, and in fact, much of the terror of the former 

 was due to the credence they gave to the baseless 

 conjectures of the latter. This feeling has by no 

 means died out, to judge from what one hears and 

 reads with regard to recent comets, but its nature 

 has perhaps slightly changed. Formerly such " wars, 

 pestilences and the death of princes " as occurred 

 shortly after the apparition of a comet were 

 attributed on the sufficient principle of post hoc, ergo 

 propter hoc, combined with the idea that all things 

 had direct effect upon human destinies (the 



Figure 239. Comet 1908 III (Morehouse). 



P. J. Melotte and C. R. Davidson, Royal Observatory, 



Greenwich. 1908, Sept. T 14 h 56 m G.M.T. Position of 



Comet: R.A. 3 h 3 m ; Decl. + 69° 38'. Reflector: Ap. 30-in. 



(0-762m); F.L. 1 1 -ft. 5-in. (3 -48m). Exp. 60 mins. 



unexpected apparitions formerly inspired, whilst 

 the calculations and verifications by returns, as 

 well as discoveries of the last generation, have to 

 some extent satisfied our curiosity as regards some 

 of the phenomena presented by them, yet other 

 problems have arisen demanding solution for which 

 the data we at present possess are inadequate. 

 The regular return of certain well-known comets, 

 such as Halley's and Encke's, though on the one 

 hand affording ample demonstration of the justice of 

 the principles and methods employed by astronomers 

 for the determination of their orbits, yet on the 

 other hand, even for these comets, unexplained, 

 though small deviations from their calculated paths 

 afford material for speculation as to the nature of 

 other agencies besides gravitation affecting their 

 motion. Other comets there are, however, which 

 have failed altogether to return, notwithstanding the 

 great increase of accuracy in our knowledge of their 

 orbits, whilst for those that do return, as well as for 

 new comets, the remarkable changes of form that 



s "*S v \ o^ \* \\ ; . V v*\ ^ v < 





FIGURE 240. Comet 1908 III (Morehouse). 



E. E. Barnard, Yerkes Observatory. 1908, Oct. l d 19 h 15™ 



G.M.T. Position of Comet: R.A. 21 h ; Decl. + 71°. Bruce 



Doublet Lens: Ap. 6-in. (0-153m); F.L. 50-3-in. (l-28m). 



Exp. 65 min. 



233 



