that "it is quite impossible for Trade Unions in general to effect any permanent increase of wages," there is much force in his conclusion, that "every rise of wages which one body secures by mere exclusive combination, represents a certain extent, sometimes a large extent, of injury to the other bodies of workmen."[31] In so far as Unions of skilled workers limit their numbers, they increase the number of competitors for unskilled work; and since wages cannot rise when the supply of labour obtainable at the present rate exceeds the demand, their action helps to maintain that "bare subsistence wage," which forms a leading feature in "sweating." Are we then to regard Unions of low-skilled workers as quite impotent so long as they are beset by the competition of innumerable outsiders? Can combination contribute nothing to a solution of the sweating problem? There are two ways in which close combination might seem to avail low- skilled workers in their endeavours to secure better industrial conditions. In the first place, close united action of a large body of men engaged in any employment gives them, as we saw, a certain power dependent on the inconvenience and expense they can cause to their employers by a sudden withdrawal. This power is, of course, in part measured by the number of unemployed easily procurable to take their place. But granted the largest possible margin of unemployed, there will always be a certain difficulty and loss in replacing a united body of employés by a body of outsiders, though the working capacity of each new-comer may be equal to that of each member of the former gang. This power belonging inherently to those in possession, and largely dependent for its practical utility on close unity of action, may always be worked by a trade organization to push the interests of its members independently of the supply of free outside labour, and used by slow degrees may be made a means of gaining piece by piece a considerable industrial gain. Care must, however, be taken, never to press for a larger gain than is covered by the difficulty of replacing the body of present employés by outside labour. Miscalculations of the amount of this inherent power of Union are the chief causes of "lock-outs" and failures in strikes.