. SOLAR DYNAMICS— SOME NEW ASTRONOMY. 309 



two processes are conceivable. One by two pulls from different directions, 

 having different centers of force, on different sides of the center of the revolv- 

 ing orb. The other by a pull and a push from the same direction, having 

 such different centers of force. For a while I favored the first of these. Now 

 it is rejected, for two reasons. First, it seems manifest that all attracting 

 forces affecting an orb would have a common center. Second, as the satellites 

 are subject to these pulls from different directions, they too should revolve if this 

 caused axial revolutions. On the other hand if axial revolutions are caused 

 by repulsion, first, only hot bodies will cause these revolutions. So we have it. 

 The planets under the rule of the sun all revolve ; the satellites under the rule of 

 the cool planets do not, but, held as by a strong grip, they move around, as that 

 grip causes them to move. Second, if the axial revolutions are caused by repul- 

 sion, the rapidity of the revolution will be affected, first by the force of the repul- 

 sion, and second, by the length of the diameter of the revolving orb; as this will 

 afford more leverage to the diverse forces. The student of astronomy will see 

 that the axial revolutions seem to harmonize with a law growing out of these prin- 

 ciples. It may be asked why grant that attraction and repulsion, the pull and 

 the push, have different centers of force in the revolving planet ? If where there 

 is most heat there is most repulsion, and where least heat most attraction, the 

 repulsion will always be strongest on the afternoon side of the planet. With more 

 push on the one side what can we have but axial revolution. And the rapidity 

 of the revolution must be determined in great measure by the factors above 

 named. 



While studying the movement of the planets diagrams were freely used, dia- 

 grams of movement at various rates and in many different directions. And here 

 much may be learned. You may conceive of the Sun as moving on any hne 

 passing through its own center ; assume that it is moving at a certain rate, and 

 you may diagram the movement then required of the solar system. The move- 

 ment on any line requires a diagram of its own different from any other. For 

 example, if the earth moves in the plane of the ecliptic, there is but one line on 

 which the Sun can be moving, viz : that of the intersection of the ecliptic with 

 the plane of the solstitial colure. Again, if the echptic is made up of a succession 

 of parallel planes, there is but one line on which the Sun can be moving, viz : 

 the line on the solstitial colure perpendicular to the plane of the ecliptic. So 

 also any given velocity requires a diagram of its own. Any change of direction, 

 or any change of velocity requires a change of the diagram representing the 

 movement of the system. The diagrams here given on Plate I represent the 

 movement of the earth if the Sun moves in the plane of the celestial equator on the 

 line of its intersection with the solstitial colure, and at a velocity of twenty-seven 

 miles per second. Fig. i is a horizontal view as seen from the north. Fig. 2 is 

 a perpendicular view as seen looking down from above. In Fig. i, at perihelion 

 the earth is north, and at aphelion south of the line, as seen in Fig. 2, In Fig. 

 2, at the vernal equinox the earth is above the line, and at the autumnal equinox 

 b elow it, as seen in Fig. i. The figures on Plate II include the Moon's move- 

 ment, and give us a hint on the cause of apogeal advances and regressions. 



