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



my own experimentally obtained velocities in various rocks 

 long previously obtained, but appear to me wholly irrecon- 

 cilable with those assumed as resulting from the Hallet's- 

 Point observations. Is this probable ? or is it not much more 

 likely that some grave and still undiscovered sources of fallacy 

 and error exist in these experiments, on which I have felt it 

 incumbent on me thus to animadvert? 



Physical infirmity has prevented my examining the subject 

 with that fulness I could have desired ; loss of sight has com- 

 pelled me to confine myself to placing before General Abbot, 

 and scientific men in general, some of the difficulties which 

 his Hallet's-Point experiments present to me and, I must 

 suppose, to all competent physicists. 



L. On the Nebular Hypothesis. — VIII. Criteria. By Pliny 

 Earle Chase, LL.l)., S.P.A.S., Professor of Philosophy 

 in Haverford College. 



[Continued from p. 297.] 



THE views of astronomers, respecting the mode of action 

 in world-building, have been various and vague. No 

 one appears to have put upon record any numerical calcula- 

 tions, undertaken with a view crucially to test the nebular 

 hypothesis, or any suggestions as to the proper way to make 

 such calculations. 



Statements have been made, at different times, by investi- 

 gators who thought that observed velocities might be explained 

 by the results of nebular condensation ; but no one, except 

 Ennis*, has given us any means of judging on what grounds 

 the belief rested. It seems likely that they all looked upon 

 the formation of planetary rings as a merely superficial phe- 

 nomenon, that their studies were limited to the direct action 

 of living forces, that they used no adequate criteria for distin- 

 guishing between nebular and meteoric influences, and that 

 their methods often, if not always, virtually assumed the very 

 principles which they sought to prove. 



Herschelf, somewhat obscurely, intimated the possibility 

 that nuclei might be simultaneously formed at different depths 

 within the body of the nebula, by the action of particles of 

 different densities ; Peirce, Alexander, Hill, Wright, Kirk- 

 wood, and myself discovered various planetary harmonies 

 which point unmistakably to such synchronous internal and 

 external activities ; yet no one seems to have thought of 

 the likelihood that interior portions would acquire a greater 



* 'Origin of the Stars' ; and Phil. Mag. April 1877, pp. 262-271. 



t Outlines of Astronomy, §§ 871-2. 



