He had it forthwith translated into Arabic, under the title of "Al-magest." The collections thus acquired sometimes became very large; thus the Fatimite Library at Cairo contained one hundred thousand volumes, elegantly transcribed and bound.

Among these, there were six thousand five hundred manuscripts on astronomy and medicine alone.

The rules of this library permitted the lending out of books to students resident at Cairo.

It also contained two globes, one of massive silver and one of brass; the latter was said to have been constructed by Ptolemy, the former cost three thousand golden crowns.

The great library of the Spanish khalifs eventually numbered six hundred thousand volumes; its catalogue alone occupied forty-four.