*42. Constituent Elements: the Law.*--The elements of which this constitution is to-day composed have been classified in various ways. For present purposes they may be gathered in five principal categories. In the first place, there are treaties and other international agreements, which in Great Britain as in the United States are invested with the character of supreme law of the land. In the second place, there is a group of solemn engagements which have been entered into at times of national crisis between parties representing opposed, or contracting, political forces. Of such character are the Great Charter, the Petition of Right, and the Bill of Rights. A third and larger category comprises parliamentary statutes which add to or modify governmental powers or procedure. Statutes of this type include clearly the Habeas Corpus Act of 1679, the Act of Settlement of 1701, the Septennial Act of 1716, Fox's Libel Act of 1792, the Reform Acts of 1832, 1867, and 1884, the Municipal Corporations Act of 1835, the Parliamentary and Municipal Elections Act of 1872, the Local Government Acts of 1888 and 1894, and the Parliament Act of 1911. In the fourth place there is the Common Law, a vast body of legal precept and usage which through the centuries has acquired fundamental and immutable character. The first three elements mentioned, i.e., treaties, solemn political engagements, and statutes, exist solely, or almost so, in written form. The rules of the Common Law, however, have not been reduced to writing, save in so far as they are contained in reports, legal opinions, and, more particularly, authoritative decisions of the courts, such as those (p. 043) on the rights of jurymen, on the prerogative of the crown, on the privileges of the houses of Parliament and of their members, and on the rights and duties of the police.