MISCELLANEOUS PROBLEMS 135 



THE CORONA AND THE ZODIACAL LIGHT 



These I look upon as parts of the same phenome- 

 non, the former being the spray, and the latter the 

 spreading mist, from the perpetual seething Niagara 

 of the sun. Yet spray and mist not of water, but of 

 the more* ethereal elements such a>s helium, nebnlinm, 

 and hydrogen, which by the violence of the sun's com- 

 motion have been temporarily expelled beyond the pale 

 of his controlling attraction. Or, in other words, they 

 form a veritable nebula, of the most extreme tenuosity, 

 having its origin, not in one great explosion involving 

 the destruction of our snn, but in those minor eruptions 

 that are normal and, so 1o speak, functional to it. 



NKIUTLA AND STAR SPECTRA 



The manner of the formation of nebulae as just 

 described seems to me to supply the key to the pecu- 

 liarities of (heir spectra. For the freshly liberated 

 gases will be expelled to unequal distances, and the 

 lighter (dements the farther. The outer envelopes of 

 the nebula should therefore, if this reasoning be cor- 

 rect, consist largely of hydrogen and similar gases; and 

 if the envelopes be sulTiciently dense so as to be opaque 

 to the Ijght of the other incandescent elements ranged 

 behind them, the predominance of such lines in celestial 

 spectra, should cease to surprise. (liven sufficient al- 

 lowance of time in which to act, gravitation would dis- 

 pose the elements in the saint 1 order, that is, the lighter 

 on the outside. 



The double spectra of stars are never visible except 

 where- two bright stars are knowingly examined at one 

 time, as in the case of binaries, or where there is evi- 

 dence of some special eruption in progress on the body 

 under examination. Tn the latter case the confusion 



