It must, at any rate in modern days, be a written constitution, for its very foundation is the "Federal pact" or contract; the constitution must define with more or less precision the respective powers of the central government, and of the State governments of the central legislature and of the local legislatures; it must provide some means (e.g., reference to a popular vote) for bringing into play that ultimate sovereign power which is able to modify or reform the constitution itself; it must provide some arbiter, be it Council, Court, or Crown, with authority to decide whether the Federal pact has been observed; it must institute some means by which the principles of the constitution may be upheld, and the decrees of the arbiter or Court be enforced against the resistance (if need be) of one or more of the separate States. These are not the accidents but the essential features of any Federal constitution; and are found under the constitution of the Canadian Dominion and of the Swiss Confederacy, no less than under the constitution of the United States. They all depend on the simple, but often neglected fact, that a Federal constitution implies an elaborate distribution and definition of political powers; that it is from its very nature a compromise between the claims of rival authorities, the Confederacy and the States, and that behind all the mechanism and artifices of the constitution there lies, however artfully concealed, some sovereign power which must have the means both to support the principles of the constitution and, when occasion requires, to modify its terms. Hence almost of necessity flow some further results. Under a federation the law of the land must be divided into constitutional laws (or, in other words, articles of the constitution), which can be changed, if at all, only with special difficulty, say by an appeal to the popular vote or by a constituent assembly, and ordinary laws which may be changed by the central Congress or by the separate assemblies of the States. The powers both of the central Parliament and of the local parliaments, depending as they do upon the constitutional compact, must be limited. Neither the National Assembly of Switzerland nor the Congress of the United States have anything like the sovereign power of the British Parliament: the same thing is obviously true of the Cantonal or State Assemblies. Such are, under one form or another, the essential characteristics of a Federal Government. A confederation of which England and Ireland formed a part would further of necessity exhibit a feature not to be found in the United States. The authority of the Confederacy would in reality mean the power of one State--namely, Great Britain. No artificial distribution of the whole country into separate States would get rid of a fact depending upon laws or facts of nature beyond the reach of constitutional arrangements. [Sidenote: Advantages of Federalism to England.]