210. It will be seen that in this chapter we have regarded the universe, not as a collection of matter, but rather as an energetic agent--in fact, as a lamp. Now, it has been well pointed out by Thomson, that looked at in this light, the universe is a system that had a beginning and must have an end; for a process of degradation cannot be eternal. If we could view the universe as a candle not lit, then it is perhaps conceivable to regard it as having been always in existence; but if we regard it rather as a candle that has been lit, we become absolutely certain that it cannot have been burning from eternity, and that a time will come when it will cease to burn. We are led to look to a beginning in which the particles of matter were in a diffuse chaotic state, but endowed with the power of gravitation, and we are led to look to an end in which the whole universe will be one equally heated inert mass, and from which everything like life or motion or beauty will have utterly gone away. FOOTNOTES: [7] This fact seems to have been known at a comparatively early period to Herschel and the elder Stephenson. [8] This remark is due to Sir William Thomson. [9] Mayer and Waterston seem first to have caught the rudiments of this idea. CHAPTER VI. _THE POSITION OF LIFE._ 211. We have hitherto confined ourselves almost entirely to a discussion of the laws of energy, as these affect inanimate matter, and have taken little or no account of the position of life. We have been content very much to remain spectators of the contest, apparently forgetful that we are at all concerned in the issue. But the conflict is not one which admits of on-lookers,--it is a universal conflict in which we must all take our share. It may not, therefore, be amiss if we endeavour to ascertain, as well as we can, our true position. _Twofold nature of Equilibrium._ 212. One of our earliest mechanical lessons is on the twofold nature of equilibrium. We are told that this may be of two kinds, _stable_ and _unstable_, and a very good illustration of these two kinds is furnished by an egg. Let us take a smooth level table, and place an egg upon it; we all know in what manner the egg will lie on the table. It will remain at rest, that is to say, it will be in equilibrium; and not only so, but it will be in stable equilibrium. To prove this, let us try to displace it with our finger, and we shall find that when we remove the pressure the egg will speedily return to its previous position, and will come to rest after one or two oscillations. Furthermore, it has required a sensible expenditure of energy to displace the egg. All this we express by saying that the egg is in stable equilibrium. _Mechanical Instability._