Prof. P. E. Chase on the Nebular Hypothesis. 451 



Calorifiques,"* says : — " Je ferai remarquer, avant de terminer, 

 que l'etude des spectres calorifiques d'absorption, faite avec 

 des corps portes a diverses temperatures, peut et doit conduire 

 a la connaissance de lois physiques reliant les phenomenes 

 d'association et de dissociation des corps aux phenomenes calo- 

 rifiques et lumineux." In another paper recently presented 

 to the French Academy, " Sur le Rapport des deux Chaleurs 

 Speeifiques d'un Graz " f, M. Ch. Simon deduces the theore- 

 tical ratio G : c : : 1*4 : 1. The first attempt at a solution of 

 the problem upon a priori grounds, appears to haye been Pro- 

 fessor ^sewcomb'sj, who foundfrom the hypothesis of actual col- 

 lisions, the ratio 5 : 3 if the particles were hard and spherical, or 

 4 : 3 if they were hard and not spherical ; the second, my own§ , 

 based on the general consideration of all internal motions, which 

 led to the ratio 1*4232 : 1 ; the third, M. Simon's, which took 

 account of rotations and neglected other internal vibrations. 



No surer test of any hypothesis has ever been suggested 

 than its furnishing a successful anticipation, or prediction, of 

 facts or phenomena that were previously unknown. 



The harmonic progression which starts from Jupiter's centre 

 of linear oscillation as a fundamental unit, and which has 4 for 

 its denominator-difference, was taken as the ground for such a 

 prediction, in the communication which I read to the Ameri- 

 can Philosophical Society on the 2nd of May, 1873 1|. Kirk- 

 wood had, a short time before, computed a probable orbit for 

 " Vulcan," which satisfactorily represented the second interior 

 term of the series ; and this accordance was one of the prin- 

 cipal sources of the confidence with which I ventured upon a 

 publication of the prediction. 



Forty-one days afterwards, on the 19th of June, De la Rue, 

 Stewart, and Loewy communicated to the Royal Society cer- 

 tain conclusions, based upon three sets of sun-spot observa- 

 tions, taken in three different years, and extending over periods 

 respectively of 145, 123, and 139 days. Those observations 

 indicated some source of solar disturbance at # 267 of Earth's 

 mean radius vector, which represented the first interior term 

 of my series and gave the first conclusive verification of my 

 prediction. In announcing this fact to the Society, I pre- 

 sented three nearly identical series — the first being determined 

 solely by Jupiter, the second by Earth, and the third by rela- 

 tions of planetary and solar masses^!. I gave precedence to 

 the first of these series, both because of Jupiter's predominant 

 importance, and because of the many planetary harmonies 

 which are determined by Jupiter's mean perihelion**. 



* Cpmptes Rendus, lxxxiii. pp. 1102-4, December 4, 1876. 



t Ibid. p. 727, October 16, 1876. % Proc. Araer. Astr. Soc. v. p. 112. 



§ Proc. Soc. Phil. Amer. xiv. p. 651. || Ibid. xiii. p. 238. 



U Ibid. pp. 470, 472. ** Ibid. p. 239. 



2G2 



