l68 REPORTS ON INVESTIGATIONS AND PROJECTS. 



tenability of any hypothesis of the planetesitnal order. The possible sources 

 of planetesimal organization are then discussed. Four states of organization 

 of free molecules are found to be required by a rigorous application of the 

 kinetic theory of gases to gaseous spheroids aud to atmospheres, the first 

 being the familiar collisional or truly gaseous state; the second, the state of 

 the elliptical, or fountain-like movement of molecules above the collisional 

 spheroid recognized by Stoney; the third, a system of molecules in quaqua- 

 versal revolutions around the collisional spheroid, and the fourth, a planet- 

 esimal system surrounding the equatorial tract of the collisional spheroid 

 when in rotation. The distribution of these is discussed and their relations 

 of equihbrium with one another, together with the application of these 

 equilibria to varying stages of evolution. In their application to the evolu- 

 tion of contracting gaseous spheroids, it is shown that the centrifugal com- 

 ponent of revolution at the equator can rarely, if ever, become equivalent to 

 the centripetal acceleration of gravity, as the result of simple contraction, 

 but that previous to reaching that stage the molecules of the collisional 

 spheroid must pass into the three other systems of organization. The paper 

 contains an ampler statement of the planetesimal hypothesis than has been 

 previously published, with new discussions of certain points, among which 

 are the significance of the present slow rotation of the sun, and of the 

 obliquity of its axis, out of which springs a suggestion relative to the 

 -possible origin of binary stars. In the disposal of the ancestral planetary 

 :family of the sun is found a possible origin of comets and meteorites. 



Taper II. — On the Probability of a Near Approach of tivo Suns and on the Orbits of 

 Material Ejected front them under the Stimulus of their Mutual Tidal Disturbances 

 By F. R. MOULTON. 



The treatment of the first part of the theme consists of the determination, 

 so far as the imperfect data will permit, of the probability of the near 

 approach of two suns. In the treatment of the second part, after some 

 considerations relative to the nature of the tidal disturbances, the pertur- 

 bations produced by one of the two bodies upon the material ejected from 

 the other are considered at length mathematically. The results of the com- 

 putations of the paths of the ejected material in the cases selected are given, 

 and are illustrated by plottings. Forty-eight such cases in which varying 

 assumptions are made relative to the positions, paths, and sizes of the two 

 suns are treated. The aggregate period through which the computations 

 of perturbations extend exceeds 200 years. Such general deductions are 

 drawn as the nature and number of cases investigated warrant. Among 

 these is the conclusion that in many cases the ejected material is left by the 

 disturbing sun, when it has receded to an ineffective distance, moving about 

 the parent sun in elliptical orbits whose eccentricities do not exceed some of 

 those found iu the orbits of the planetoids. 



