438 Literary and Scientific Intelligence : [Oct. 



traordinary rapidity ; and by examining its diameter at every favour- 

 able opportunity, and laying down the measures by a projected curve, 

 I found the curve to be very nearly a straighl line, indicating a uni- 

 form rate of increase ; and by tracing back this line to its intersection 

 with the axis, I was led, at the time, to this very singular conclusion, 

 viz. that on the 21st of January, at 2h. p. m., the disc must have been 

 a point — or ought to have had no magnitude at all ! in other words, at 

 that precise epoch some very remarkable change in the physical con- 

 dition of the comet must have commenced. So far all was specula- 

 tion. But in entire harmony with it is the following fact communi- 

 cated to me no longer ago than last month by the venerable Olbers, 

 whom I visited in my passage through Bremen, and who was so good 

 as to show me a letter he had just received from M. Boguslawski, 

 Professor of Astronomy at Breslau, in which he states that he had 

 actually procured an observation of that comet on the night of the 21st 

 of January. In that observation it appeared as a star of the sixth magni- 

 tude — a bright concentrated point, which showed no disc, with a magni- 

 fying power of 140! And that it actually was the comet, and no star, 

 he satisfied himself, by turning his telescope the next night on that 

 point where he had seen it. It was gone ! Moreover, he had taken 

 care to secure, by actual observation, the place of the star he observed ; 

 that place agreed to exact precision with his computation ; that star 

 toas the comet, in short. Now, I think this observation every way 

 remarkable. First, it is remarkable for the fact, that M. Boguslawski 

 was able to observe it at all on the 21st. This could not have been 

 done, had he not been able to direct his telescope point blank on the 

 spot, by calculation, since it would have been impossible in any other 

 way to have known it from a star. And, in fact, it was this very thing 

 which caused Mr. Maclear and myself to miss procuring earlier observ - 

 ations. Iam sure that I must often have swept, with a night-glass, 

 over the very spot where it stood in the mornings before sunrise ; and 

 never was astonishment greater than mine at seeing it riding high in 

 the sky, broadly visible to the naked eye, when pointed out to me by a 

 notice from Mr. Maclear, who saw it with no less amazement on the 

 24th. The next remarkable feature is the enormously rapid rate of 

 dilatation of the disc and the absorption into it of all trace of the sur- 

 rounding nebula. Another, is the interior cometic nucleus. All these 

 phenomena, while they contradict every other hypothesis that has ever 

 been advanced, so far as I c;m see, are quite in Accordance with a 

 theory on the subject which I suggested on the occasion of 

 some observations of Biela's comet, — a theory which sets out from 



