From Herr Leibniz we have heard that there is a Property of bodies called vis viva , and another called the quantité d’avancement , both of which are conserved through all collisions and transformations of a system. The first is equal to the product of the mass and the square of the velocity, and the second is simply the product of the mass and the velocity. At the beginning of time the Universe was endowed with a certain fund of both, which neither waxes nor wanes with time, but is merely exchanged among bodies, like silver pennies in a market-place. Which leads one to ask: is Power like the vis viva , and the quantité d’avancement , i.e., is it conserved by the Universe? Or is it like shares of a stock, which may have great value one day, and be worthless the next?