320 ANNUAL OF SCIENTIFIC DISCOVERY. 



the hands of M. Kriiger. A star of the 8.9 mag., No. 21,258 of La- 

 lande's Catalogue, and another of the 9. raag., No. 17,415-6 in the Cata- 

 logue of Oeltzen, had been pointed out by Argelander as remarkable 

 from their large amount of proper motion, in the latter case amounting 

 to 1".2 annually. Thirty-six comparisons of the former with two other 

 suitably placed stars yielded an amount of parallax = 0". 260, with a 

 probable error of 0".020. The latter star, from a mean of forty-five 

 similar comparisons, showed a parallax = 0".247, with a probable error 

 of 0".021. This, if confirmed by future measures, would bring these 

 inconspicuous objects actually nearer to us than Polaris, Arcturus, or 

 even the magnificent Sirius himself, and must suggest very remarkable 

 speculations as to the probable structure of the Universe. London 

 Intellectual Observer. 



VISIBILITY OF STARS IN THE PLEIADES. 



In a late number of the Notices of the Royal Astronomical Society 

 the Astronomer Royal, Mr. G. Airy writes as follows : To the 

 greater number of star-gazers, with what are commonly called good 

 eyes, I believe that Ovid's remark as to the visible number of Pleiades 

 still applies: ' Quse septem did, sex tamen esse solent' (which are 

 wont to be called seven, yet are but six.) I find, however, that one 

 of my family habitually sees seven, and on rarer occasions twelve." On 

 the clear evening of Feb. 15th, 1863, a map of the visible stars was 

 drawn from ocular view, and, on comparing it with a map drawn from 

 Bessel's measures, Mr. Airy had no difficulty in identifying the stars 

 with six numbered by Bessel. 



THE PHENOMENA OF COMETS. 



The great difficulty which confronts us in every attempt to investi- 

 gate the nature of comets is the absence of all satisfactory analogy. 

 No one can have watched an opposition of Mars without being con- 

 vinced of a general similarity between the constitution of that globe 

 and our own ; and even in Jupiter and Saturn, though belonging to 

 another planetary type, the evident and complete control of gravity, 

 the provision for day and night, and the existence of an atmosphere of 

 varying transparency and constant mobility, form points of contact, so 

 to speak, of considerable significance. But in the case of comets, with 

 the sole exception of the influence of gravity over the denser portions 

 of the mv ss, analogy breaks down altogether, and direct observation 

 has hitherto, for the most part, brought out nothing more than a series 

 of marvellous and unaccountable facts, maintaining obstinately the se- 

 cret of the law, which no doubt unites them into a harmonious and 

 beautiful whole. We have not as yet any adequate information as to 

 the composition of the nucleus ; whether, even in the most brilliant 

 comets, it ever attains a state of actual solidity, or whether all may not 

 be as unsubstantial as one of our own clouds, which, at an equal dis- 

 tance and under suitable illumination, would no doubt reflect a very 

 vivid light ; in fact, as to the real nature of the material of comets, be- 

 yond that extraordinary attenuation of mass which makes their attrac- 

 tion imperceptible, even in their closest known appulses to other bod- 

 ies, we have not a single idea. That they are ponderable is certain, 

 or they would not obey the attraction of the sun ; but when we would 



