Note C — CHAPTERS ON THE STARS. By Professor SIMON NEWCOMB, U. S. N. THE SPECTRA OF THE STARS.

As this principle is not universally understood, it may be well to remark that it results immediately from Kirchoff’s law of the proportionality between the radiating and absorbing powers of all bodies for light of each separate wave-length. When a body, even if gaseous in form, is of such great size and density that light of no color can pass entirely through it, then the consequent absorption by the body of light of all colors shows that throughout the region where the absorption occurs there must be an emission of light of these same colors. Thus light from all parts of the spectrum will be emitted by the entire mass.