Now, since human muscles are soon wearied in action, and since motion is the only thing required of men in the production of commodities, they naturally look around for outside help in this matter; and the first help they lighted on for moving things was the domestic animals, the ox and ass and horse, doubtless domesticated in the very beginnings of society; and as these can be used in so many different places, and for such a variety of purposes, and are so cheaply reared, they are exceedingly useful as a motive power, and will probably never be superseded as such. Inanimate auxiliaries in moving things into right position for the production of commodities, such as the water-wheel and wind-mill, were undoubtedly brought into use much later; and much later still, steam and electricity and other more subtle and recondite natural agents. All of these helps, whether animate or inanimate, do but cause simple motions of the same kind as those caused by the human hand. The most ponderous engine merely reduplicates that which the arm of a child is capable of; while in point of delicacy and firmness of touch, perhaps no machinery can subdivide and apply this motion so skilfully as the human fingers can. It is said that some of the lace made wholly by hand is finer and more delicate than any yet woven by machinery, although the introduction of machinery into lace-making has cheapened lace products in general to a small fraction of their former cost. What we commonly call "_Power_," then, by whatever instrumentality furnished, is simple auxiliary motion, additional to that of physical human Labor. Commodities are produced in unlimited quantity and variety by such labor, assisted by the free forces of nature applied by means of animals and implements, which are capital. But such labor is irksome as well as wearisome, and is never expended except in view of a reward, which is secured only from the sale of the finished commodity. (c) Reserved Capital. We must examine the nature of Capital with care, and follow its varied forms without confusion, because it is the only other factor besides labor in the production of commodities, that has to be paid for out of their sale.