The secondary sources are those that are compiled from a study of the original sources, or from other secondary works, or from both, as is more likely to be the case. This class of material is very abundant, and varies greatly in character and value because of the striking difference in authorship, style, and purpose. It is always necessary, therefore, carefully to discriminate the wheat from the chaff and to be able easily to recognise the "earmarks" of a reliable authority. Many of the works produced by modern scientific scholarship are excellent in every respect, and, in many fields of historical study, absolutely indispensable. Secondary sources may be divided as follows: A.--Written works: I.--History: 1. General treatises based upon either primary sources, or secondary materials, or both. 2. Encyclopedias and dictionaries. 3. Monographs, essays, and articles. II.--Fiction: 1. Novels. 2. Poetry. 3. Drama. B.--Unwritten: I.--Oral traditions and reports. II.--Transmitted rites and ceremonies. III.--Works of art copied from originals. The earliest account of the history of the Christian Church extant is the New Testament. The "Memoirs" of Hegesippus, a converted Jew of the second century, is the first known effort to record the growth of the Church, but all his books are lost.[15:1] Eusebius, the Greek bishop, called the "Father of Church history," wrote a comprehensive _Ecclesiastical History_ to 324. Socrates, Sozomen, and Theodoret, each after his own ideal, continued the narrative of Eusebius. Rufinus translated the work of Eusebius into Latin and continued it to 395, while Epiphanius translated Socrates, Sozomen, and Theodoret into Latin and brought the record to 518. Theodorus and Evagrius were also continuators of these early works. Sulpicius Severus, a Gallic monk of noble birth, penned a fabulous chronicle of little worth. The Middle Ages produced little of real value in the field of Church history. The chronicles represent the best output. A few scholars of the Eastern Church, the Byzantine historians, the annalists of the Latin Church, and several specialists like Gregory of Tours and the Venerable Bede, complete the list. The lives of saints, however, abound.