But the distance which the water will travel during this second will be the difference between the distance which it would have ascended if there had been no gravity forcing it down, and the distance which it would have descended if there had been no momentum driving it up; and, at the end of the second, the rate of its motion upwards, or its velocity, will be proportionally slower. Thus, at the end of the first second, the water has spent a certain portion of its momentum in overcoming its gravity. And as there is nothing to make good the loss, it would, if left to itself, travel more slowly, or over a less distance, in the second second than it tended to do in the first. But though the momentum of the water is diminished, its gravity, weight, or tendency to fall downwards, for a given distance in a second, remains exactly what it was, and operates in the course of the second second to exactly the same extent as in the first. Hence, at the end of the second second, the distance through which the water travels upwards is still smaller, and its velocity is still more diminished. It is obvious that, however great the disproportion between momentum and gravity to start with, gravity must gain the day in the long run under these circumstances. The store of momentum will be used up; and, after a momentary rest, the water, reduced to the condition of a body without support, will begin to be carried downwards by the unopposed action of gravity. The case is similar to that of a boy sculling a boat, the bows of which are suddenly seized and the boat thrust violently backwards by a strong man. The boat will go stern-foremost rapidly, at first, but every stroke of the boy’s oar at the stern will retard its backward motion; until, at length, the stock of momentum conferred upon it by the man’s thrust will be completely exhausted in working against the boy, and the boat, after a momentary rest, will resume its onward course. The distance to which the boat will be propelled backwards will evidently depend upon the amount of muscular power which the man, as it were, suddenly capitalizes in the boat, and which the boat then slowly pays out. We call people who possess much muscular or other power energetic; and we estimate their =energy= by the obstacles they overcome, or, in other words, by the =work= they do. In the present illustration the man’s energy would be measured by the distance to which the boat was propelled before it stopped. It is easy to transfer this conception of energy, as the power of doing work, to inanimate things; and thus when a body in motion overcomes any kind of obstacles in its way, parting with its momentum and more or less coming to rest in the process, we say that it has =energy= and that it does =work=.