248 THE POPULAR SCIENCE MONTHLY. 



tronomical Society, that no object has thrown more light on the gen- 

 eral nature of cometic bodies than the comet known as Biela's. I pro- 

 pose now to give a brief sketch of the history of this interesting body, 

 and then to consider the reasons why astronomers expect that during 

 the last week of November, 1879, there will be a display of shooting 

 stars as the earth passes through the comet's track. 



In the year 1826 Biela discovered a comet, the path of which was 

 calculated by Gambart, a French astronomer, insomuch that, accord- 

 ing to the usual rule in such cases, the comet should be called Gam- 

 bart's, not Biela's. It was found to revolve around the sun in a period 

 of about six and two thirds years. It was not a conspicuous body — in 

 fact, it has seldom been much more than barely visible under the most 

 favorable conditions by the naked eye. Yet it differed from most tel- 

 escopic comets in showing not only a nucleus and a coma, but a tail 

 also. In 1832, 1839, and 1846, this comet returned to the earth's 

 neighborhood, and on two of these occasions it was well seen. In 1839 

 it was so situated as to be lost in the sun's rays. In fact, at every 

 third return astronomers knew that it would be hopeless to search for 

 the comet. Thus, it was discovered in 1826, and well seen in 1832, 

 but not seen and not even looked for in 1839. So, again, it was seen 

 in 1846 in its calculated place, and again in 1852, but it was not looked 

 for in 1859. In 1866 and 1872 it should have been visible, but, as will 

 presently be explained more fully, it was not seen. In this present 

 year, 1879, supposing all had gone on as in the forty preceding years, 

 the comet would not have been visible, passing too near the sun's place 

 in the sky. Astronomers have been set to search for it this year (but 

 quite fruitlessly), because there were reasons to believe that, if seen at 

 all, the comet would not be seen on its former track. But we must 

 not pass to this part of the comet's history until the strange circum- 

 stances connected with former returns and with former expected re- 

 turns of the comet to visibility have been briefly considered. 



In the year 1846, when Biela's comet was well seen, it divided — or 

 rather, after having apparently been single, it was seen to be divided 

 — ^into two distinct comets, each having coma, nucleus, and a short 

 tail of its own. These two comets traveled along side by side until 

 they passed out of view ; but in 1852 both returned into view, though 

 the distance between them was then greatly increased. Whether in 

 1859 the companion comets would have been seen had the earth been 

 more favorably situated, is not known. The comet was not even 

 looked for in that year, so hopeless did the search seem for so faint an 

 object, close as the comet then was to the sun's apparent place in the 

 sky. But in 1866 the comet should have been seen as favorably as in 

 1846. The superintendent of the " Nautical Almanac " published an 

 ephermis of the comet's motions — in other w^ords, he stated where the 

 comet was to be looked for day after day, and a number of the most 

 skillful practical observers in Europe searched carefully for it, but it 



