274 HUBERT ANSON NEWTON. 



After a careful discussion of the evidence Professor Newton reached 

 the conclusion that " we must regard as almost certain (on the 

 hypothesis of an equable distribution of the directions of absolute 

 motions), that the mean velocity of the meteoroids exceeds con- 

 siderably that of the earth ; that the orbits are not approximately 

 circular, but resemble more the orbits of comets." 



This last sentence, which is taken from the abstract published in 

 the American Journal of Science in 1865, and is a little more 

 definitely and positively expressed than the corresponding passage 

 in the original memoir, indicating apparently that the author's 

 conviction had been growing more positive in the interval, or at 

 least that the importance of the conclusion had been growing upon 

 him, embodies what is perhaps the most important result of the 

 memoir, and derives a curious significance from the discoveries which 

 were to astonish astronomers in the immediate future. 



The return of the November or Leonid shower in 1865, and 

 especially in 1866, when the display was very brilliant in Europe, 

 gave an immense stimulus to meteoric study, and an especial 

 prominence to this group of meteoroids. "Not since the year 

 1759," says Schiaparelli, " when the predicted return of a comet first 

 took place, had the verified prediction of a periodic phenomenon 

 made a greater impression than the magnificent spectacle of 

 November, 1866. The study of cosmic meteors thereby gained the 

 dignity of a science, and took finally an honorable place among 

 the other branches of astronomy." Professor J. C. Adams, of 

 Cambridge, England, then took up the calculation of the perturba- 

 tions determining the motion of the node. We have seen that 

 Professor Newton had shown that the periodic time was limited to 

 five sharply determined values, each of which with the other data 

 would give an orbit, and that the true orbit could be distinguished 

 from the other four by the calculation of the secular motion of the 

 node. 



Professor Adams first calculated the motion of the node due to the 

 attractions of Jupiter, Venus, and the Earth for the orbit having a 

 period of 354*6 days. This amounted to a little less than 12" in 

 33'25 years. As Professor Newton had shown that the dates of the 

 showers require a motion of 29' in 33*25 years, the period of 354' 6 

 days must be rejected. The case would be nearly the same with a 

 period of 376*6 days, while a period of 180 or 185*4 days would give 

 a still smaller motion of the node. Hence, of the five possible periods 

 indicated by Professor Newton, four were shown to be entirely 

 incompatible with the motion of the node, and it only remained to 



* Schiaparelli, Entwurf einer astronomischen Theorie der Sternschnuppen, p. 55 



