A word may be added about the ‘enumerated’ and the ‘residuary’ powers. The object of enumerating the powers of any authority is to the limit it. Where, then, a federal constitution enumerates the powers of the Centre, as in the U.S.A., the object clearly is to limit its powers as against the units, and enable the latter to retain all the rest ; conversely, where it enumerates the powers of the units, as in Canada, the object is to limit their powers as against the Centre. In general, therefore, it is true to say that the greater the ‘reserve of powers’ with the units, the more markedly federal is the State whose constitution permits such reserve to them.