Oometary Light. 285 



idea, might consist of vapour in a vesicular state, like our 

 clouds, which do not polarize, while the coma and tail were in 

 a gaseous and polarizing condition. Huggins, however, by 

 his more refined and critical mode of analysis, may be con- 

 sidered to have decided this question. An important remark 

 of his should not be omitted here. He thinks that the dark 

 spaces which so frequently intervene between the multiple 

 envelopes of comets, may represent an intermediate condition 

 of the matter originally derived from the nucleus, when it has 

 ceased to be self luminous, but, from still retaining its gaseous 

 state, is capable of reflecting but little light in its transition 

 to a more visible condition, analogous to fog or cloud. Many 

 curious questions of detail, however, remain to be considered, 

 and it is to be hoped that before long the near approach of 

 some magnificent and fully-developed comet, such as that of 

 1744, which nearly rivalled the splendour of Venus, and was 

 visible to the naked eye at noon-day, may give full scope to 

 the employment of his extraordinary means of investigation. 

 Even before the arrival of such a phenomenon, some out of 

 the ordinary profusion of smaller comets may furnish materials 

 for keeping us on the alert. Bight of them, of very various 

 sizes, were recorded in 1858, and the recent scarcity may be 

 fairly considered the precursor of renewed abundance. 



The comet whose light Huggins so successfully analysed, 

 though not a brilliant, is in some respects a remarkable one. 

 D' Arrest observes that it is the sole instance hitherto known 

 of retrograde motion combined with shortness of period. The 

 latter he fixes at 3930.] days, the course all lying within the 

 orbit of Saturn. Pechyle has given 53 years, Oppolzer about 

 30, but D' Arrest considers the elements very uncertain. At 

 its first discovery, by Tempel, its motion was so rapid that it 

 passed in 5h. through 2°, or about four times the breadth of 

 the moon. D' Arrest remarks that its present orbit may be 

 of modern date, and that it is more and more probable that 

 comets of short period have not long pertained to our system, 

 and are rapidly tending to dissolution. This he thinks is 

 indicated by the unquestionably decreasing brilliancy of 

 Encke's and Faye's comets, and notices Kepler's anticipated 

 description of the fate of that of Biela, when he suggests the 

 possibility of their division and dissipation. 



The total loss, as it would seem, of the latter comet, though 

 not an unprecedented occurrence, as that of 1770 never ap- 

 peared again according to computation, is an event of con- 

 siderable significance. It is an additional proof that the stamp 

 of mutability has been impressed upon all created matter. 

 From the comparatively small dimensions of its orbit, and the 

 known character of the space which it had to traverse and the 



