86 H. A. Newton— The Story of Biela? s Comet. 



of New Haven, well-known to many of you from his connec- 

 tion with the New Haven Bank. Professor Hubbard was 

 graduated two years before (in 1843) at this college, and was 

 now Professor in the Naval Observatory 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 Professor 

 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 labor some of the results 

 of astronomy must be wrought out. In your school days 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, I think, even four thousand fig- 

 ures 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 increased 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 I tell you that he hated shams. 



Positions in 1852. — In 1852 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 afterward. 



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. Professor Hubbard found that he could 

 not tell which comet of 1852 was preceding and which follow- 

 ing, in 1845. One supposition agreed as well with the obser- 

 vations 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 D, 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 degrees 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 



