the direct supervision of the inventor, went with an accuracy that has not since been surpassed, the difficulty of reproducing them rendered the invention valueless. But the great example of this particular truth is to be found in a certain fact connected with the history of the steam-engine—a fact which is little known, whose significance has never been realised, and which I shall mention a little later on. It may thus be said with regard to the production of wealth generally, that it will be limited in proportion to the exceptionally skilled labour it requires, whilst it will be increased in proportion to the exceptional ability that is applied to it. [Sidenote ◆1 We shall now be able to describe Capital accurately as _Ability_ controlling _Labour_.] ◆¹ The difference, then, between Ability and Labour must be now abundantly clear. As a general rule, there is the broad difference on the surface, that the one is mainly mental and the other mainly muscular; but to this rule there are many exceptions, and the difference in question is accidental and superficial. The essential, the fundamental difference from a practical point of view is, that whilst Labour is the exertion of a single man applied to a single task, Ability is the exertion of a single man applied to an indefinite number of tasks, and an indefinite number of individuals. [Sidenote ◆1 It is, of course, understood that this definition applies only to Capital used so as actually to make Labour more productive, not to Capital wasted.]