278 HUBERT ANSON NEWTON. 



the results of careful statistical calculations on the effect of per- 

 turbations on orbits of comets originally parabolic. It corroborates 

 the more general statements of the paper " On the Origin of Comets," 

 giving them a precise quantitative form. One or two quotations 

 will give some idea of the nature of this very elaborate and curious 

 memoir, in which, however, the results are largely presented in the 

 form of diagrams. 



On a certain hypothesis regarding an original equable distribution 

 of comets in parabolic orbits about the sun, it is shown that " if in 

 a given period of time a thousand million comets come in parabolic 

 orbits nearer to the sun than Jupiter, 126 of them will have their 

 orbits changed " by the action of that planet " into ellipses with 

 periodic times less than one-half that of Jupiter; 839 of them will 

 have their orbits changed into ellipses with periodic times less than 

 that of Jupiter; 1701 of them will have their orbits changed into 

 ellipses with periodic times less than once and a half that of Jupiter, 

 and 2670 of them will have their orbits changed into ellipses with 

 periodic times less than twice that of Jupiter." A little later, Pro- 

 fessor Newton considers the question, which he characterizes as 

 perhaps more important, of the direct or retrograde motion of the 

 comets after such perturbations. It is shown that of the 839 comets 

 which have periodic times less than Jupiter, 203 will have retrograde 

 motions, and 636 will have direct motions. Of the 203 with retro- 

 grade motion, and of the 636 with direct motion, 51 and 257, respec- 

 tively, will have orbits inclined less than 30 to that of Jupiter. 



We have seen that the earliest of Professor Newton's more important 

 studies on meteors related to the Leonids, which at that time far 

 surpassed all other meteoric streams in interest. One of his later 

 studies related to another stream which in the mean time had acquired 

 great importance. The identification of the orbit of the Andromed 

 meteors with that of Biela's comet, which we have already mentioned, 

 gave these bodies a unique interest, as the comet had been seen to 

 break up under the influence of the sun. Here the evolution of 

 meteoroids was taking place before our eyes; and this interest was 

 heightened by the showers of 1872 and 1885, which in Europe seem 

 to have been unsurpassed in brilliancy by any which have occurred 

 in this century. 



The phenomena of each of these showers were carefully discussed 

 by Professor Newton. Among the principal results of his paper on 

 the latter shower are the following:* 



The time of the maximum frequency of meteors was Nov. 27, 1885 

 6 h. 15 m. Gr. m. t. The estimated number per hour visible at one 



* Amer. Jour. 8ci., ser. 3, vol. xxxi, p. 409. 



