192 WARRED UPHAM, M.A., F.G.S.A., ON THE NEBULAR AND 



formed by a combined outward and rotatory movement implies a 

 preexisting body that embraced the whole mass. In harmony with 

 this, an ancestral solar system has been postulated — a system 

 perhaps in no very essential respect different from the present 

 one . . . 



" To this conception of an ancestral sun with an undefined 

 antecedent history as a star, question will arise at once as to a 

 sufficiency of energy for the sun's maintenance through such a 

 prolonged history. . . . This objection is based on the 

 assumption that the sun's heat and light are derived almost wholly 

 from self -compression, as urged by Helmholtz. This self-compression 

 has usually been computed on the basis of certain limiting 

 assumptions, the validity of which is open to question. . . 

 The extraordinary energies displayed by radio-active substances are 

 doubtless but an initial demonstration of immeasurable energies 

 resident in other forms of matter and in the constitution of the 

 sidereal system and competent for its maintenance for unassignable 

 periods. . . . 



" . . No appeal is here made to collisions as a source of the 

 parent nebula of the solar system, but only to an approach of the 

 ancestral sun to another large body, and this approach is not 

 assumed to have been very close. . . . 



" Our present sun shoots out protuberances to heights of many 

 thousands of miles, at velocities ranging up to 300 miles per second 

 and more. If it were not for the retarding influence of the immense 

 solar atmosphere, some of these outshoots would doubtless project 

 portions of themselves to the outer limits of the present system, 

 and perhaps in some cases quite beyond it, for the observed 

 velocities sometimes closely approach the controlling limit of the 

 sun's gravity, if they do not actually reach it. . . If with 

 these potent forces thus nearly balanced the sun closely approaches 

 another sun or body of like magnitude, suppose one several times 

 the mass of the sun, since it is regarded as a small star — the gravity 

 which restrains this enormous elastic power will be relieved along 

 the line of mutual attraction, on the principle made familiar in the 

 tides. At the same time the pressure transverse to this line of 

 relief is increased. Such localized relief and intensification of 

 pressure must, it is believed, result in protuberances of exceptional 

 mass and high velocity. According to the well-known tidal 

 principle, these exceptional protuberances would rise from opposite 

 sides, and herein lies the assigned explanation of the prevalence 

 of two diametrically opposite arms in the spiral nebulae. 



" Nothing remotely approaching a general dispersion of the 

 ancestral sun seems to be required. The present planets and their 

 satellites altogether amount to about one-seven-hundredth part of 

 the mass of the system. Simply to supply the required planetary 

 matter, the protuberances need include but this small fraction of 



