Page:Principles of Political Economy Vol 1.djvu/55

Rh greater. He exerts this power either by availing himself of natural forces in existence, or by arranging objects in those mixtures and combinations by which natural forces are generated; as when by putting a lighted match to fuel, and water into a boiler over it, he generates the expansive force of steam, a power which has been made so largely available for the attainment of human purposes.

Labour, then, in the physical world, is always and solely employed in putting objects in motion; the properties of matter, the laws of nature, do the rest. The skill and ingenuity of human beings are chiefly exercised in discovering movements, practicable by their powers, and capable of bringing about the effects which they desire. But, while movement is the only effect which man can immediately and directly produce by his muscles, it is not necessary that he should produce directly by them all the movements which he requires. The first and most obvious substitute is the muscular action of cattle: by degrees the powers of inanimate nature are made to aid in this too, as by making the wind, or water, things already in motion, communicate a part of their motion to the wheels, which before that invention were made to revolve by muscular force. This service is extorted from the powers of wind and water by a set of actions, consisting like the former in moving certain objects into certain positions in which they constitute what is termed a machine; but the muscular action necessary for this is not constantly renewed, but performed once for all, and there is on the whole a great economy of labour.

§ 3.Some writers have raised the question, whether nature gives more assistance to labour in one kind of industry or in another; and have said that in some occupations labour does most, in others nature most. In this, however, there