To these may be added the names of Molinos van Espen and Colbert, Bishop of Montpellier. It is difficult, in an examination of the complete lists, to arrive at any principle or basis on which the compilers made their selections. Of forty-one Protestant writers whose names were placed on the Index during one sitting of the Index Congregation in May, 1757, sixteen were Germans, ten, Hollanders, eleven, Frenchmen, and four, Englishmen. At the same session, were prohibited the entire series of the theological writings of Hugo Grotius. Between 1757 and 1821, there is no instance in the Roman Indexes of the use in connection with the name of an author of the term _Opera omnia_, although as a fact in a number of cases every book produced by some particular author was included under its own title. Between the years 1821 and 1827, the authors whose complete works were thus specifically condemned by title include G. Mordai, David Hume, and Colin de Plancy. In 1852, were added, among other names, those of V. Giorberti, Proudhon, and Sue. In 1862, the prohibition included Dumas father and son, Georges Sand, Murger, Stendhal, Balzac, Champfleury, Feydeau, and Soulié. In 1876, three names are to be noted, Vera, Spavente, and Ferrari. The works of John Locke called for special attention in two of the Indexes of the first half of the 18th century. The reading or possession of these books is forbidden under penalty of excommunication, _sub anathemate_. In 1610, was prohibited the treatise that had been published in the previous year by Hugo Grotius, _Mare liberum S. de jure quod Batavis competit ad Indicana commercia_. The entry was alphabeted under _H_. The title has been preserved in the later Indexes of the 19th century under the proper heading, Grotius. The purpose of the treatise was to contest, on the ground of natural right and of the _Jus gentium_, the monopoly, which had secured the support of Alexander VI, of the Spaniards and Portuguese over certain lines of sea trade. The Pope had taken the ground that his authority was sufficient to institute trade monopolies either by land or by sea. If the Pope were in a position to grant ownership of territories and of peoples, the smaller matter of the connecting trade might naturally be assumed as the conclusion. Grotius, however, asserts that no authority vested in the Pope had given to the Spaniards the control of the Indies (of the West) and that such control as had come to the Spaniards had been secured through force of arms and not through the papal diploma.