For the possession of the requisite skill, implying as it does a certain natural capacity, and an expenditure of time and money not within the power of the poorest classes, forms a practical limit to the number of applicants.

Moreover, in many trades, though by no means in all, restrictions are placed by the Unions upon the number of apprentices, with the object of limiting the number of those who should from year to year be qualified to compete for work.

In other trades where no rigid rule to this effect exists, there is an understanding which is equally effective.

Certain trades, such as the engineers, boiler-makers, and other branches of iron trade, place no restrictions, and in certain other trades the restrictions are not closely applied.

But most of the strong Trades Unions protect themselves in another way against the competition of unemployed.