As already mentioned, the three kinds of ether, warmth, light and sound, are not sufficient in themselves to bring into existence what in its proper sense we call 'life' in nature, i.e. the formation of single living organisms. This requires the action of a fourth kind of ether, the life-ether, ranged above the other three. We can best comprehend the life-ether's contribution to the total activity of the ether in nature by considering the interaction of the four kinds of ether with the four physical elements. We have seen that the warmth-ether has the double function of being at once the lowest ether and the highest physical element, thus acting as a sphere of reflexion for the other kinds of ether and the elements respectively. Each stage in the etheric has its reflexion in the physical, as the above table shows. Thus to the physical air the etheric light is related. (The affinity of light and air is best seen in the plant and its leaf-formation.) To bring about real changes in the material composition of the physical world requires the stronger powers of the chemical ether. Therefore it is also the first ether of which we had to speak as 'magical' ether. Its effects reach into the watery element which is already bound up with gravity, but by its own strength it cannot penetrate beyond that. The causation of material changes in the liquid sphere would in fact be all that these three kinds of ether could achieve together. Only when the power of the life-ether is added to the three others can etheric action reach as far as the sphere of solid matter. Thus the life-ether is responsible for all solid formation in nature, both in her organic and inorganic fields (the latter-crystal-formation-being the effect of external ether-action).10 It is to the action of the life-ether that nature owes the existence in her different realms of multitudes of separate solid forms. To mention an instance from our previous studies: in the same way as volcanic phenomena manifest the warmth-ether's gravity-overcoming power on a macrotelluric scale, so snow-formation illustrates the life-ether's matter-shaping might. Through its power to bind flowing action into solid form, the life-ether is related to the sound-ether in the same way as the articulated word formed by human speaking is related to the mere musical tone. The latter by itself is as it were fluid. In human speech this fluidity is represented by the vowels. With a language consisting only of vowels man would be able to express feelings, but not thoughts. To let the word as carrier of thought arise out of sound, human speech possesses the consonants, which represent the solid element in it.