From the last paragraph it will be seen that, were it not for friction and the resistance of the air, the pendulum would vibrate forever; that the energy would be indestructible. Energy is withdrawn from the pendulum to overcome these impediments, but the energy thus withdrawn is not destroyed. What becomes of it will be seen when we come to study heat and other forms of energy, which result from the motions and positions of the molecules of matter. The truth is that energy is as indestructible as matter. For the present we must admit that a given amount of energy may disappear, and escape our search, but it is only for the present. We shall soon learn to recognize the fugitive even in disguise.