394 



NA TURE 



[Feb. 25, 1886 



laterally, was not less than 50,000 miles. Again, M. Struve 

 saw it pass centrally over a star of the 9th magnitude. 

 A like star was seen' in the telescope at the same time, so 

 that he was able to say that the comet did not dim in the 

 least the one which it covered. The comet, as the figure 

 (Fig. 4) shows, was in 1832 always at a great distance 

 from the earth. 



Another 65 years brings us to 1839. The comet came 

 to perihelion, at p, in July. The earth and comet were on 

 opposite sides of the sun both before and after July, and 

 of course the comet was not seen. 



Position in 1845. — Another circuit was finished in 1 8450. 



The comet was visible then during five months, from a to 

 b (Fig. 5), or as viewed from the sun through nearly half 

 its circuit. At this time it was that the comet became 

 all at once famous. 



On December 29 Mr. Herrick (then Librarian of Yale 

 College) and Mr. Francis Bradley (then in the City Bank) 

 were watching the comet through the Clark telescope in 

 the Athenaeum tower yonder. They saw a small com- 

 panion comet beside the larger one ! What did it mean ? 

 Had the comet a satellite like the earth's moon ? Or had 

 the comet been split by some convulsion ? Two weeks 

 later the companion comet was seen by Lieut. Maury and 



Prof. Hubbard at Washington, and two days after that it 

 was seen by two or three European astronomers. 



Changes were seen in the larger telescopes that in- 

 creased the mystery. The faint companion grew in size 

 and brilliancy. Each comet threw out a tail. Then the 

 smaller one had two tails. Then the larger one had a 

 pointed, or diamond-shaped, rather than a" round head. 

 Two nuclei were seen in the larger one, and it also had 

 two tails. An arch of light was thrown over from one to 

 the other. For some days in February the companion 

 was the brighter of the two. Presently three tails were 

 seen running from the primary, and three cometary frag- 



ments (one observer says five) around its nucleus. What 

 could it all mean .' Do you wonder that astronomers were 

 excited by these wizard changes .' 



The companion comet was seen in Washington by 

 Maury and Hubbard two weeks after it was seen here by 

 Herrick and Bradley. Prof. Joseph Hubbard was the 

 son of a resident of New Haven, well known to many of 

 you from his connection with the New Haven Bank. 

 Prof. Hubbard was graduated two years before (in 1843) 

 at this College, and was now Professor in the Naval Ob- 

 servatory at Washington. He took up the study of the 

 motions of the two Biela comets as special work, outside 

 of his hours on duty. How faithfully he worked, four 

 thick manuscript volumes of figures might tell. I cannot 

 show you those books. They form, since Prof. Hubbard's 

 death, a cherished memento in the possession of a friend. 

 But I have brought another of Hubbard's volumes from 

 the College Library, one of three upon the comet of 1843, 

 in order to show you by what patient labour some of the 

 results of astronomy must be wrought out. In your school 

 da; s you called it a wondrously long sum that covered 

 both sides of the slate. On the leaves of this book there 

 are, as you see, one, two, three, and in some cases, 1 think, 

 even four thousand figures upon the page. You will, I 

 am sure, excuse me from telling in detail to-night how 

 we learn about the sizes, distances, and motions of the 

 comets. Eight or ten such volumes of figures, to be in- 

 creased in time, we hope, by the four Biela volumes, form 

 a monument to a true, devoted, gentle scholar of science. 

 You will not wonder when 1 tell you that he hated shams. 



Position in 1S52. — In 1S52 the comet was always at a 

 great distance from the earth (Fig. 6), and only to be seen 

 through the largest telescopes. The changes of size and 

 brightness of the two comets were remarkable, and as 

 they could but just be seen, sometimes one and sometimes 

 the other alone was visible ; which one it was that a 

 person saw at any time was only told by computation 

 afterwards. 



The two comets were now eight or ten times as far 

 apart as they had been seven years before. They were at 

 the point P, 1,250,000 miles apart. Prof. Hubbard found 

 that he could not tell which comet of 1852 was preceding 

 and which following in 1845. One supposition agreed as 

 well with the observations as the other. 



Perhaps the knowing ones among you have noticed that 

 the arc from the node to the point marked Jan. 10 in the 

 first diagram is too large for one month, for in 1772 the 

 earth passed the node Dec. 9. But you will notice that 

 when the comet is at n, and the large planet Jupiter is 

 near by, he draws the comet toward the plane of the figure. 

 The result is to bring the comet down to meet the earth's 

 orbit farther from P. The node thus went back from 

 Dec. 9 to Nov. 27, a distance of 12 days, or 12° in the 

 circle. The figure represents this last orbit. By the same 

 cause the inclination was reduced one-fourth, or from 17° 

 to 12". 



Since .September 1852 (with one doubted exception to 

 be spoken of), neither of the two Biela comets had been 

 seen. In 1S59 their path was to us behind the sun. In 

 1866 they should have been at the point P on January 26. 



