Turning to the gaseous condition, we realize that although even here matter retains traces of a connexion with terrestrial gravity, levity is now the dominant factor. There are three characteristics of the gaseous condition which bring this out. One is the extreme readiness of gases to expand when heated; we see here how much easier than with solid substances it is for heat to overcome the influence of gravity. The second characteristic is the property of gases, peculiar to them, of expanding spontaneously, even when not heated. Here we find gaseous matter displaying a dynamic behaviour which at lower stages occurs only under the stimulus of heat. The third characteristic is shown by the fact that all gases, unlike solids or liquids, respond with the same increase of volume to a given rise of temperature, however diverse their other qualities may be. Once gases are mixed, therefore, they cannot be separated merely by raising or lowering the temperature. Here we find the unifying effect of the cosmic periphery prevailing over the differentiating effect of terrestrial gravity.