Another weapon in the hands of unskilled combination, less calculable in its effectiveness, is the force of public opinion aided by "picketing," and the other machinery of persuasion or coercion used to prevent the effective competition of "free" labour. In certain crises, as for example in the Dock strike of 1889, these forces may operate so powerfully as to strictly limit the supply of labour, and to shut out the competition of unemployed. There can be no reason to doubt that if public authority had not winked at illegal coercion of outside labour, and public opinion touched by sentiment condoned the winking, the Dock strike would have failed as other movements of low-skilled labour have generally failed. The success of the Dockers is no measure of the power of combination among low-skilled labourers. It is possible, however, that a growing sense of comradeship, aided by a general recognition of the justice of a claim, may be generally relied upon to furnish a certain force which shall restrict the competition of free labour in critical junctures of the labour movement. If public opinion, especially among workmen, becomes strongly set in favour of letting capital and labour "fight it out" in cases of trade disputes, and vigorously resents all interference of outsiders offering to replace the contending labourers, it seems likely that this practical elimination of outside competition may enable combinations of unskilled workmen to materially improve their condition in spite of the existence of a large supply of outside labour able to replace them.