ON COMETS. 125 



(41.) Another great comet which has assumed a sort of 

 historical and political importance is that which ap- 

 peared in A.D. 1556. According to the account of 

 Gemma, it would not seem to have been a very large 

 one, as he assigns to it a tail of only four degrees long. 

 Its head, however, equalled Jupiter in brightness, and in 

 size was estimated at about one-third or one-half of the 

 diameter of the moon. It appeared about the end of 

 February, and on the i6th of March is described by 

 Ripamonte as a really terrific object. Terrific indeed 

 it might well have been to the mind of a prince prepared 

 by the most abject superstition to receive its appearance 

 as a warning of approaching death, and as specially sent, 

 whether in anger or in mercy, to detach his thoughts 

 from earthly things, and fix them on his eternal inter- 

 ests. Such was its effect on the Emperor Charles V., 

 whose abdication of the imperial throne is distinctly 

 ascribed by many historians to this cause, and whose 

 words on the occasion of his first beholding it have 

 even been recorded - 



" His ergo indidis me meafata vacant!" ^ 



the language and the metrical form of which exclamation 

 afford no ground for disputing its authenticity, when the 

 habits and education of those times are fairly considered. 

 This comet has been supposed to be periodical, and to 

 return in 291 years, on the ground of the prior appear- 

 ance of great comets in the years 975 and 1264 (at in- 

 tervals, that is, of 289 and 292 years respectively), and 

 the general agreement of their orbits, so far as could be 



