In ancient Egypt collections of hieroglyphic writings were made in temples and in the tombs of kings from the earliest known dates. Some hieroglyphics still extant bear date prior to 2000 B. C., and one papyrus manuscript has been discovered whose supposed date is 1600 B. C. What were known as the sacred Books of Thoth—forty-two in number—constituted the Egyptian encyclopædia of religion and science, and became such a fruitful source of commentary and exposition, that by the time of the Grecian conquest they had grown in number of volumes to 36,325. Of the libraries of the Greeks we have little positive knowledge, though it is abundantly asserted by late compilers that large collections of books (writings) once existed in the various Grecian cities. Pisistratus is said to have founded a library at Athens as early as 537 B. C. Strabo says that Aristotle collected the first known library in Greece, which he bequeathed to Theophrastus (B. C. 322), and which, by the vicissitude of war, finally found its way to Rome. At Cnidus there is said to have existed a special collection of works upon medicine. Xenophon speaks of the library of Euthydemus. Euclid and Plato are mentioned as book collectors. But by far the most renowned book collectors of the Greeks were the Ptolemies of Egypt, who gathered from Hellenic, Hebrew, and Egyptian sources that wonderful collection of volumes, or rolls, which became famous as the Alexandrine Library. This was composed of two libraries, one estimated at 42,800 volumes, or rolls, connected with the Academy, the other estimated at 490,000 volumes, or rolls, deposited in the Serapeum. It is said that these immense collections were regularly catalogued and kept under the supervision of competent librarians, till consumed by the Saracens at the time of their conquest of Egypt, A. D. 640.