X']2 REPORTS ON INVESTIGATIONS AND PROJECTS. 



From this conception a series of theoretical deductions weie drawn 

 forth relative to the mode of evolution of the solar sj^stem and the 

 course of the earlier history of the earth, and these were tested by 

 application to the actual facts so far as was then practicable. This 

 hypothesis was worked out, essentially as set forth in my last report, 

 in the absence of Dr. Moulton and without the advantage of free 

 conference with him. It seemed desirable, therefore, that he should 

 traverse independently the postulates and deductions from the view- 

 point of the dynamics involved. This inquiry, as stated in the accom- 

 panying report, gave results altogether favorable to the hypothesis 

 qualitatively, and this deepened the conviction that a more elaborate 

 and laborious investigation on quantitative lines would be justified. 

 Dr. Moulton has therefore undertaken, with the assistance of a com- 

 puter, to trace out the approximate course that would be pursued by 

 masses of matter ejected from the sun under the perturbing influ- 

 ence of a passing star, under different relations of mass, velocity, 

 distance, eccentricity, etc , as set forth in the accompanying report. 

 The results thus far reached indicate even greater potency in the 

 postulated conjunction of agencies than had been assigned to it, both 

 in the value of the perturbations of the ejected matter and in the 

 range of results. It appears that even if the approach of a star of 

 no greater magnitude than the sun were not nearer than the orbit of 

 Jupiter and the solar ejections were limited to the mid-distances of 

 the system, the ejected material (i) might in some cases be given 

 orbits about the sun of varying dimensions and eccentricities ; (2) 

 might in other cases be captured by the passing star and take orbit 

 of varying dimensions and eccentricities about it ; (3) might in still 

 others be given hyperbolic orbits and pass away from the control 

 of either sun, and (4) might in still others return to the sun after 

 pursuing variously perturbed courses, and by such return modify the 

 rotation of the parent body — in other words, might give essentially 

 the whole range of possible classes of results. It is therefore believed 

 that out of the very great variety of possible cases which may arise 

 from different combinations of mass, nearness of approach, eccen- 

 tricity of orbit, velocity, and longitude of ejection, cases competent 

 to produce a spiral nebula suited to evolution into a solar system may 

 be found, and that consistent conditions of origin may be definitely 

 postulated with no greater contingency in the basal assumption than 

 the passage of a star in the vicinity of the sun. 



My own work has consisted largely in the further application of 

 the sequences of the planetesimal hypothesis to the various geolog- 

 ical problems to which they are related. While an hypothesis of 

 this kind must first of all meet dynamical and astronomical tests, is 



