Page:Popular Science Monthly Volume 85.djvu/554

550 who have longest been subjected to the urgent necessity to labor. It is, accordingly, largely a matter of climate; and we find that, in general, the instinct to work diminishes from high latitudes to the tropics. This aspect of work appears as a substantially modern conception. In order to appreciate the full significance of the point of view, it will be helpful to turn our attention for a while to an entirely different field; that of physical science. There, the idea of work (and of its correlate, energy) has begun to play a role so prominent as to be in fact the center and point of departure of our apprehension of life and of the universe.

In the narrowest physical sense, "work" is exclusively mechanical work, such as that required to move an object. Such work is performed when a locomotive pulls a train or when a man lifts a load. In these cases the work is made up of two factors, first, power or force; second, path or distance. The science of physics teaches us that the work is equal to the power (or force) multiplied by the path (or distance), because the product has the peculiarity that it is equally influenced by a change in either component. If either the force or the distance be doubled, the work will also be doubled. In virtue of measuring work in this precise manner, a very important law of nature is arrived at, called the law of the conservation of work, or energy. The essence of the law is, that by no means is it possible to obtain work out of nothing, but only to obtain one kind of work out of another kind of work, under the limitation that the total work obtained can never be greater than that used to start with.

According to a familiar anecdote, Archimedes declared that if he had a lever long enough and a place to rest it on, he could move the world. He figured that he could increase the force of his effort indefinitely by indefinitely increasing the length of the lever. Every laborer who uses a crow-bar has experimental knowledge of the effect, which, at first glance, seems incompatible with the conservation law. The apparent discrepancy vanishes when we remember that the short arm of the lever moves less than the actuating hand, so that just in proportion as we increase the force do we diminish the distance through which the force is applied; the work done at the short end of the lever remaining the same as that performed by the hand at the long end. Hence, while Archimedes might indeed move the world as he imagined, yet the distance through which it moved would be so infinitesimal as to transcend observation.

In a word, we may say that work is not creatable. We must be content with that which is in the world accessible to us. Still, our whole existence depends on work, in the broader sense. Whenever anything whatever happens, work is consumed, to be transformed into that which distinguishes the new from the old condition. The significance of