To give any account, even in outline, of the subject matter of equity within the necessary limits of this article would be impossible. It will be sufficient to say here that the classification generally adopted by text-writers is based upon the relations of equity to the common law, of which some explanation is given above. Thus equitable jurisdiction is said to be exclusive, concurrent or auxiliary. Equity has _exclusive_ jurisdiction where it recognizes rights which are unknown to the common law. The most important example is trusts. Equity has _concurrent_ jurisdiction in cases where the law recognized the right but did not give adequate relief, or did not give relief without circuity of action or some similar inconvenience. And equity has _auxiliary_ jurisdiction when the machinery of the courts of law was unable to procure the necessary evidence. "The evils of this double system of judicature," says the report of the judicature commission (1863-1867), "and the confusion and conflict of jurisdiction to which it has led, have been long known and acknowledged." A partial attempt to meet the difficulty was made by several acts of parliament (passed after the reports of commissions appointed in 1850 and 1851), which enabled courts of law and equity both to exercise certain powers formerly peculiar to one or other of them. A more complete remedy was introduced by the Judicature Act 1873, which consolidated the courts of law and equity, and ordered that law and equity should be administered concurrently according to the rules contained in the 26th section of the act. At the same time many matters of equitable jurisdiction are still left to the chancery division of the High Court in the first instance. (See CHANCERY.) AUTHORITIES.--The principles of equity as set out by the following writers may be consulted: J. Story, J.W. Smith, H.A. Smith and W. Ashburner; and for the history see G. Spence, _The Equitable Jurisdiction of the Court of Chancery_ (2 vols., 1846-1849); D.M. Kerly, _Historical Sketch of the Equitable Jurisdiction of the Court of Chancery_ (1890). EQUIVALENT, in chemistry, the proportion of an element which will combine with or replace unit weight of hydrogen. When multiplied by the valency it gives the atomic weight. The determination of equivalent weights is treated in the article STOICHIOMETRY. (See also CHEMISTRY.) In a more general sense the term "equivalent" is used to denote quantities of substances which neutralize one another, as for example NaOH, HCl, 1/2 H2SO4, 1/2 Ba(OH)2.