THE BIRTH OF OUR WORLD n 



predominance of metalloids and of alkaline or earthy metals 

 the compounds of which are the lightest of all. The compounds 

 of the alkaline metals are almost soluble ; we may, therefore, 

 assume that the seas of these planets are far more saline than 

 ours, a fact which, as we shall see later on, is not without its 

 consequences. 



The present incandescent state of the sun's surface, and the 

 immense hydrogen flames that dart out from it, imply that its 

 entire mass has an extremely high temperature ; it is even 

 probable that it is in a molten state, and that its brilliancy 

 is due to solid scoria floating on the surface of the molten 

 mass. At the time when these planets were formed the 

 temperature of the sun could not have been lower than it is 

 to-day ; it is therefore certain that the sun was in a liquid, 

 if not a gaseous state, when the planets were detached. Their 

 distinctly spherical form and even their flattening at the poles 

 confirm this hypothesis. It is only much later, when the 

 atmospheric gases were freed, that their surface consolidated. 

 Such, at least, is what happened on the earth. Water then 

 formed a part of the atmosphere, the earth's surface being still 

 too hot for it to exist in a liquid state ; and as the surface cooled 

 the water gradually became precipitated, and the vaporous 

 atmosphere covering it became clearer. Venus, which is younger 

 than the Earth, nearer to the Sun, and for these reasons hotter, 

 is still in a phase where clouds absolutely conceal its surface ; 

 it therefore reflects toward us the bright light which wins such 

 admiration for the evening star, and shines even in a sky 

 illuminated by the rays of the sun — although the firmament 

 is masked for its own inhabitants who, according to the 

 pertinent observation of Henri Poincare, are perhaps still 

 unaware of the existence of the stars. Mars, on the contrary, 

 being smaller and twice our age, while Venus is only half, has 

 acquired an atmosphere of extreme limpidity. 



Jupiter, which is enormous in comparison with the Earth, 

 being 1,279 times larger, has cooled less rapidly, but it is 

 further away from the sun, and eight times older than our 

 Earth ; it is possible that water is being precipitated on its 

 surface, and that it has long since formed oceans like ours 

 whence rise clouds which seem to be distributed in bands 

 parallel to the equator by winds comparable to our trade- 



