The same 'law,' we are told, holds good in building a dam across a stream and utilising the force of water to drive a mill. The energy apparently lost in the construction is recovered in the superior ease with which we grind our corn or saw our timber. There is a confusion in the terminology here: to save energy that would otherwise be lost is not identical with recovering energy that has once been used. We make a gun, load it, and discharge a bullet against a target. What has become of the force expended? It has been transformed into heat, say the conservationists. And when the target and flattened bullet have cooled down? The energy has gone to raise the general temperature of the universe! That is a conclusion hard to believe and impossible to verify. But--granting that the individual explosions of a gun may be the 'conservation' of some antecedent power--how do we recover the initial expense of the instrument? And if not recoverable, where at least and in what form does it exist? Prior to the explosions that are represented by heated targets and the like, energy was spent in inventing and making the gun, making the ammunition, loading and aiming the piece. All these were essential to the effect--and what has become of them? Have they also gone to warm the universe? Instead of raising a stone to a height, let us carry it along horizontally till we feel the same degree of fatigue. If energy in the using is merely transformed but not lost, we should now be in possession of some power equivalent to the energy expended. But we are not--we have nothing to show for our trouble. If we construct a water-mill and fix it high and dry in the middle of a plain, instead of under a fall of water, we get no return for the energy expended. By such a law as the conservation of energy, and with the usefulness of a properly placed mill as the measure of compensation, we should receive an equivalent return no matter where the mill is placed. What has _place_ to do with the action of a universal law? Instead of raising the stone or carrying it horizontally, let us find it near the edge of a precipice and roll it over. There is no proportion between the push that launched the stone, and the force it exhibits on reaching the foot of the precipice. How is the equivalence of energy maintained in this case? It will be replied that the force now at work is gravitation. If so, it was gravitation that brought down the first stone on the post--not any energy transferred from us to the stone. The raising of the stone put us in a position to use the force of gravity, just as climbing the precipice put us in a position to roll the stone over the edge of it. Such considerations as these make this 'law' incredible to me. But when I pass from the explanation to the concrete facts, I have no difficulty in understanding them. It is the law that is obscure--not the facts.