Usually designated by the first letter of the Hebrew alphabet, is one of the most valuable of ancient MSS. of the Greek New Testament. On the occasion of a third visit to the convent of St. Catherine, on Mount Sinai, in 1859, it was discovered by Dr. Tischendorf. He had on a previous visit in 1844 obtained forty-three parchment leaves of the LXX., which he deposited in the university library of Leipsic, under the title of the Codex Frederico-Augustanus, after his royal patron the king of Saxony. In the year referred to (1859) the emperor of Russia sent him to prosecute his search for MSS., which he was convinced were still to be found in the Sinai convent. The story of his finding the manuscript of the New Testament has all the interest of a romance. He reached the convent on 31st January; but his inquiries appeared to be fruitless. On the 4th February he had resolved to return home without having gained his object. "On that day, when walking with the provisor of the convent, he spoke with much regret of his ill-success. Returning from their promenade, Tischendorf accompanied the monk to his room, and there had displayed to him what his companion called a copy of the LXX., which he, the ghostly brother, owned. The MS. was wrapped up in a piece of cloth, and on its being unrolled, to the surprise and delight of the critic the very document presented itself which he had given up all hope of seeing. His object had been to complete the fragmentary LXX. of 1844, which he had declared to be the most ancient of all Greek codices on vellum that are extant; but he found not only that, but a copy of the Greek New Testament attached, of the same age, and perfectly complete, not wanting a single page or paragraph." This precious fragment, after some negotiations, he obtained possession of, and conveyed it to the Emperor Alexander, who fully appreciated its importance, and caused it to be published as nearly as possible in facsimile, so as to exhibit correctly the ancient handwriting. The entire codex consists of 346 1/2 folios. Of these 199 belong to the Old Testament and 147 1/2 to the New, along with two ancient documents called the Epistle of Barnabas and the Shepherd of Hermas. The books of the New Testament stand thus: the four Gospels, the epistles of Paul, the Acts of the Apostles, the Catholic Epistles, the Apocalypse of John. It is shown by Tischendorf that this codex was written in the fourth century, and is thus of about the same age as the Vatican codex; but while the latter wants the greater part of Matthew and sundry leaves here and there besides, the Sinaiticus is the only copy of the New Testament in uncial characters which is complete. Thus it is the oldest extant MS. copy of the New Testament. Both the Vatican and the Sinai codices were probably written in Egypt. (see VATICANUS.)