able to see its surface through the encompassing clouds. Mars will not answer our purpose, for it seems to have long passed the stage in which volcanic energy was a prominent manifestation on its surface. We cannot examine the details on Venus sufficiently to know how far it might supply the information we seek, and the same may be said of the other planets. They give us but little aid.
_-_Figure_40.jpg)
Fig. 40.—Solar Protuberance. April 6, 1892.
There is, indeed, only one globe in the system which can be cited, and that is the sun. Of course, there is but very slight resemblance between the present condition of the sun and the condition of our earth at the early period referred to. The sun is so highly heated that it probably does not contain any solid matter whatever, and therefore is very unlike what our earth must have been at the time of which we speak when its exterior parts had already become solid, if not actually cold. But
