I50 T. C. CHAMBERLIN 



1. Stimulus to eruptivity, as well as generation of tangential 

 motion in the projected matter assigned to a passing star. 



a) Star of medium mass and distance (one to five astronomical 



units, more or less). Original type, tested mathematically 



by half-hundred concrete trial cases. 

 h) Giant star (in mass); distance great, tidal effect small, 



tangential effect large. 

 c) Diminutive star, distance relatively small, tidal effect 



relatively large, tangential effect relatively small. 



2. Stimulus to eruptivity, as well as generation of tangential motion 

 in the projected matter, assigned to some non-stellar body, a stray 

 planet for example. Approach to sun quite close, perhaps pene- 

 trating its Roche limit; tidal effect relatively great; adequacy of 

 tangential effect less obvious, but assigned to the closeness with 

 which the solar projections were shot out behind the passing body. 



3. Stimulus to eruptivity, as well as generation of tangential motion 

 in the projected matter, assigned to a special concentration of gravitative 

 stress in open space arising from two or more related bodies of large 

 mass, for example, the center of gravity between two stars, or the 

 concentrated gravity-stress of star clusters in certain forms of ar- 

 rangement. 



4. Actuating forces arising wholly within the solar system. Pro- 

 jectile effects assigned to eruptive and projective forces within the 

 sun; the tangential effects assigned to co-operative action of 

 positive and negative centers in the sun as suggested above. 

 Little more than a suggested possibility. 



CRITICAL PHASES OF THE EVOLUTIONARY PROCESS 



Let us follow that form of the planetesimai hypothesis whose 

 working competency has been most fully tested. According to this 

 the nuclei of the planets and satellites arose from solar eruptions — 

 those of the planets from the central masses of such eruptions, 

 those of the satelhtes from subsidiary masses that closely accom- 

 panied these and kept within their spheres of control. It is our 

 special task to follow the nuclei of the four little bodies under 

 study from their source in the sun to their organized states, having 

 especiall}^ in mind those features that bear on the segregation of 



