THE FUEL OF THE SUN. 9o 



by the termination or aphelion portion of these excursions, or 

 of such a number of them as should be sufficient to produce a 

 visible result. 



Again, speaking of the asteroids, in Chapter 14, I state that 

 " I should have expected a still greater elongation and eccentric- 

 ity in some of them, and such orbits may have existed ; but 

 an asteroid with an orbit of cometary eccentricity that would 

 in the course of each revolution cross the paths of Mercury, 

 Venus, the Earth, and Mars, in nearly the same plane, and 

 dive through the thickly scattered zodiacal cluster, both in 

 going to the sun and returning from it, would be subject to 

 disturbances which would continue until one of two things 

 occurred. Its tangential force might become so far neutralized 

 and its orbit so much elongated, that finally its perihelion dis- 

 tance should not exceed the solar radius, when it would finish 

 its course by returning to the sun. On the other hand, its 

 tangential velocity might be increased by heavy pulls from 

 Jupiter, when slowly turning its aphelion path, and be similarly 

 influenced by friendly jerks in crossing the orbits of the 

 inferior planets ; and thus its orbit might be widened, until it 

 ceased periodically to cross the path of any of the planets by 

 establishing itself in an orbit constantly intermediate between 

 any two. Having once settled into such a path, it would 

 remain there with comparative stability and permanency. If I 

 am right in this view of the dynamical history of these older 

 ejections, all the long elliptical paths of zodiacal particles, 

 meteorites, or asteroids, would thus in the course of ages 

 become eliminated, and the remaining orbits would be of 

 planetary rather than cometary proportions." 



A little reflection on the above-stated laws of dissociation 

 will show that the maximum violence of hydrogen explosion 

 will not occur at the birth of the ejections, but afterwards, 

 when the dissociated gases have been already hurled beyond 

 the sphere of restraining vapors. If my explanation is correct, 

 the typical form of a solar prominence should be that of a 

 spreading tree with a tall stem. At first the least resistance to 

 radiation arid consequent explosive combination must be in the 

 vertical direction, as this will afford the shortest line that can 

 be drawn through the thickness of the surrounding jacket of 

 resisting vapor ; but when raised above this envelope, the dis- 

 sociated gases, cooled by their own expansion and compara- 

 tively free to radiate in all directions except downward, will 

 explode laterally as well as vertically, and thus spread out into 



