20 Tribune Extras Pamphlet Series. 



hemisphere that, instead of presenting the appearance 



It had when it approached the sun, it appeared 

 not only without t:iil. but even without auy Lead. 

 It appeared as u small bright speck, like 

 the small central part within that crescent, -which 

 you see here. Nothing distinguished that comet 

 from a star except the fact that it was moving slowly 

 over the heaveus, and as days passed on it increased, so 

 that iu 17 days it increased 70 times in size. It seemed 

 as if it were trying to develop a long tail, but 

 it passed away before a tail had been developed. 

 It was noticed that there seemed to be a power in tlie 

 euu to raise from the nucleus of that comet vaporous 

 matter, which was, again, swept away by the sun; and 

 Sir John Herschel at that time said that, in his opinion, 

 that was the nature of the economy of a comet that 

 mat 1 1 r is so raiM.-d, and that the sun has power over that 

 matter to repel it. 



EVIDENCES OF THE REPULSION THEORY. 



You notice I a in dwelling on that fact of repulsion. I 

 want 10 show tliat power of the sun in repelling matter 

 from :t I will now deal with one of those small comets, 

 ve-ry curious, indeed, in their history. We have here all 

 the evidence we can get, although it is not very striking. 

 In the year 1770 a small comet made Its appearance, 

 which, having been watched for a time, was found not 

 to be traveling in one of these long oval paths, such as 

 are here presented ; but in a path which, instead of 

 liaving one of these long periods, was completed 

 within a period of 5J years. It was called, from the 

 vaiin* of the astronomer, Lexell's comet. It was never 

 seen agnin. Astronomers then were led to inquire 

 what had become of this comet. Tracing it 

 back, they found it was in a path so near to 

 Jupiter that the giant power of that planet ar- 

 rested it in its course, and sent it out on a patli entirely 

 different from what it was before. It was useless to look 

 for it. This question then arose: How was it that this 

 comet of very striking appearance had naver been 

 seen betorel Traveling in a period of five and a hair 

 years, how was tt it had never been seen 1 They traced 

 it back and calculated its path, and Uiey found that the 

 ea-ne iriaui hand which sent that comet away had intro- 

 duced it. That comer, in 1CC7, approached quite close to 

 Jupiter; so close, In fact, as to intrude itself among its 

 eatellitcs. Jupiter is not the planet to stand any non- 

 sense of that sort, and so compelled it to follow another 

 course. Another five and a half years, and another five 

 and a half years, and then it was again seized by Jupiter, 

 and sent outside of the solar system, and where it has 

 gone nobody knows. There is rather a curious fact in 

 connection with the history of the French revolution. 

 Blanqui, a it-publican, was imprisoned, and ho took 

 It into his bend to write about comets, and something 

 made him look on Jupiter as a sort of policeman, and 

 be descriii'-d Jupiter as beiug always patrolling ou the 

 watch for con:ei. When they came near he drove 

 them Into the perilous straits, and It was well 

 f or thi) coiui-ts if they could escape from 

 that time forth. But still there is one 

 point about this comet of Lexell worth notice. It had 

 cone into the midst of Jupiter's satellites. The satel- 



lites are not large objects, and !f th^ comet bad 

 mass he could disturb them ; but instead of that til 

 those satellites are still traveling the path they tmd 

 before that comet had arrived, and we learn, there- 

 fore, that that comet at any rate was mere vapor, 

 had no power and no weight, although it was much 

 larger even than Jupiter. It had uo powcr.no weight 

 or attractive influence to disturb those little satellites 

 which Jupiter manages so easily. 



Now we come to another comet that seen in 1843, 

 which is really interesting, as traveling on the siiortest 

 period of any comet we know of, a period of three years 

 and four mouths. It is noteworthy on this account, that 

 this little comet seems to be getting closer and closer to 

 the sun. traveling always on a shorter and shorter 

 period. It is apparently retarded by the influence of 

 some matter occupying space. It may seem a strange 

 fact, to say that it is retarded, and yet it is traveling 

 more and more quickly. But that is the eflVct, of retarda- 

 tion iu any instance. If our earth is to be retarded, the 

 effect will be that our earth will travel more and moro 

 rapidly, because the effect of the retardation would lie to 

 get the earth nearer and nearer to the sun, and ;ill ih3 

 time she is being retarded by resistance she would bo 

 hastened by the pull of the sun drawing her inward, ,iud 

 when she arrives so that she travels on the path of 

 Venus she will travel as fast as Venus, and when tr.ivel- 

 ing the path of Mercury, she will travel as fast as Mer- 

 cury, then faster and faster until in the course ol tirno 

 she will fall on the sun. This comet is traveling faster 

 and faster on a smaller and smaller orbit. 



COMET OF 1818. 



But 1 pass from that, and KO to one. the facts 

 by which are among the most curious I mean the cornet 

 which was discovered in 1820. It was carr',,lly 

 watched, and it was then found that this coni'-t Had 

 been seen before by Caroline Herschel and others, and 

 a path was assigned to it, having u period of six years 

 and eiffht months. Now this comet was in the hrst 

 place remarkable, because its path cresset the earth's 

 path; and, indeed, on the next return, in 1832, astrono- 

 mers announced that that comot would actually cross 

 the earth's path, and many thought that that meant 

 that there would be a collision, and great alarm was 

 excited. A member of the Paris Academy 

 said It was Imprudent for astronomers to make such 

 an announcement, for in 1771 announcement*! made in 



