Page:Sir William Herschel, his life and works (1881).djvu/170

148 account for all the shades of darkness seen in the penumbra. Ascending currents from the solar surface will elevate certain regions, and may increase the solar activity near by, and will thus give rise to faculæ, which shows to be elevated above the general surface. It will not be necessary to give a further account of this theory. The data in the possession of the modern theorist is a thousand-fold that to be derived from observations, and, while the subject of the internal construction of the sun is to-day unsettled, we know that many important, even fundamental, portions of his theory are untenable. A remark of his should be recorded, however, as it has played a great part in such theories:

"That the emission of light must waste the sun, is not a difficulty that can be opposed to our hypothesis. Many of the operations of Nature are carried on in her great laboratory which we cannot comprehend. Perhaps the many telescopic comets may restore to the sun what is lost by the emission of light."

Arguments in favor of the habitability of both sun and moon are contained in this