The former was called the parent library, and the latter, being, as it were, the offspring of the first, was called the daughter.
Ptolemy Philadelphus, who interested himself very greatly in collecting this library, wished to make it a complete collection of all the books in the world.

He employed scholars to read and study, and travelers to make extensive tours, for the purpose of learning what books existed among all the surrounding nations; and, when he learned of their existence, he spared no pains or expense in attempting to procure either the originals themselves, or the most perfect and authentic copies of them.

He sent to Athens and obtained the works of the most celebrated Greek historians, and then causing, as in other cases, most beautiful transcripts to be made, he sent the transcripts back to Athens, and a very large sum of money with them as an equivalent for the difference of value between originals and copies in such an exchange.
In the course of the inquiries which Ptolemy made into the literature of the surrounding nations, in his search for accessions to his library, he heard that the Jews had certain sacred writings in their temple at Jerusalem, comprising a minute and extremely interesting history of their nation from the earliest periods and also many other books of sacred prophecy and poetry.

These books, which were, in fact, the Hebrew Scriptures of the Old Testament, were then wholly unknown to all nations except the Jews, and among the Jews were known only to priests and scholars.

They were kept sacred at Jerusalem.