Page:Popular Science Monthly Volume 1.djvu/163

Rh separates the intense heat of the interior portions of the sun from the cold surrounding space. He holds to powerful ascending and descending currents, which result here and there in breaks and dispersions by which openings are made to the gaseous interior, giving the appearance of spots; to which Kirchhoff replies that an incandescent interior, at so high a temperature, would certainly be luminous.

In 1858, before the views of either Kirchhoff or Faye were announced, or spectrum analysis had been applied to the subject, Mr. Herbert Spencer published an article on "Recent Astronomy and the Nebular Hypothesis," in which he anticipated some of the most important results that have been arrived at since by others. He took the ground that the sun is still passing through that incandescent stage which all the planets have long ago passed through, the lateness of his cooling being due to the immensely greater ratio of his mass to his surface. He supposes the sun to have now reached the state of a molten shell with a gaseous nucleus; and that this shell is ever radiating its heat, but is sustained at its high temperature by the progressive condensation of the sun's total mass.

As respects the solar atmosphere, Mr. Spencer said in 1858:

This view was sustained in the most remarkable manner, by the subsequent discoveries, through spectrum analysis, of the metals iron, calcium, magnesium, sodium, chromium, and nickel, in a gaseous state in the atmosphere of the sun.

As respects the solar spots, in the article above quoted, Mr. Spencer suggested that they were due to cyclonic action. He has subsequently developed this view, which is now regarded as the most rational explanation we have of the cause of solar spots. In the latest edition of "The Heavens," by Guillemin, published last year, translated by Lockyer, and edited by Proctor, after a review of the subject, and an examination of all the theories that have been