Still there may be exceptional cases, as that of Ireland, where an unreasonable number of poor companies, in a poor country, wrangling among themselves, and giving a bad service at an excessive cost, intensify social and political evils, where the arguments in favour of a State purchase may outweigh the objections; and the extent and nature of State control over British railways is always a question fairly open to discussion. In other departments, the supply of articles such as water and gas, and the enforcement of sanitary conditions, are probably best left to local authorities: in the latter case, under some central supervision to see that the duty is not evaded. Wherever neglect involves danger to others, as in the case of small-pox and other contagious epidemics, it is clear that the decision cannot be left to individuals, and the State is bound to interfere to enforce rational precautions. So also the State is bound to undertake trades which are essential for the protection of the nation against foreign enemies. Our dockyards and arsenals may, and doubtless do, often make mistakes and turn out expensive work; but we could not safely leave the building of ironclads and supply of cannon solely to private enterprise, for there is no such large and steady demand for such articles as would induce a number of private firms to erect works and keep up establishments adequate to supply the wants which might arise in an emergency. In all such matters, therefore, of national defence we must put up with a certain amount of drawbacks incidental to State management, and confine ourselves to endeavouring to reduce them to a minimum. And this is to a great extent within the power of the nation and its Parliament, by applying common-sense principles of business to national expenditure, and seeing that while on the one hand we get as nearly as possible a pound’s worth of work for every pound spent, on the other hand we do not spend nineteen shillings uselessly, because some Chancellor of the Exchequer wants to gain momentary popularity by the ‘penny wise and pound foolish’ economy of docking the extra shilling off the necessary estimates. In private life a man gets on by knowing when to spend as well as when not to spend, and true economy has no greater foe than spasmodic parsimony alternating almost certainly with spasmodic extravagance. It would be easy to multiply instances, for there are few phases of political and practical life to which the principle of polarity does not apply, where extremes are not false, and where there is not a good deal to be said on both sides of the question. But the very obviousness of the principle makes it difficult to deal with it generally without degenerating into commonplace, while to trace its application exhaustively in any one instance would require a volume. Those who wish to pursue the subject further will do well to study the works of Herbert Spencer, where they