Hypatia was the author of three works on mathematics, all of which have been lost, or destroyed by the ravages of time. One of these was a commentary on the _Arithmetica_ of Diophantus. The original treatise--or rather the part which has come down to us--was found about the middle of the fifteenth century in the Vatican Library, whither it had probably been brought after Constantinople had fallen into the possession of the Turks. This valuable work, as annotated by the great French mathematicians Bachet and Fermat, gives us a good idea of the extent of Hypatia's attainments as a mathematician. Another of Hypatia's works was a treatise on the _Conic Sections_ by Apollonius of Perga--surnamed "The Great Geometer." Next to Archimedes, he was the most distinguished of the Greek geometricians; and the last four books of his conics constitute the chief portions of the higher geometry of the ancients. Moreover, they offer some elegant geometrical solutions of problems which, with all the resources of our modern analytical method, are not without difficulty. The greater part of this precious work has been preserved and has engaged the attention of several of the most illustrious of modern mathematicians--among them Borelli, Viviani, Fermat, Barrow and others. The famous English astronomer, Halley, regarded this production of Apollonius of such importance that he learned Arabic for the express purpose of translating it from the version that had been made into this language. A woman who could achieve distinction by her commentaries on such works as the _Arithmetica_ of Diophantus, of the _Conic Sections_ of Apollonius, and occupy an honored place among such mathematicians as Fermat, Borelli, and Halley, must have had a genius for mathematics, and we can well believe that the glowing tributes paid by her contemporaries to her extraordinary powers of intellect were fully deserved. If, with Pascal, we see in mathematics "the highest exercise of the intelligence," and agree with him in placing geometers in the first rank of intellectual princes--_princes de l'esprit_--we must admit that Hypatia was indeed exceptionally dowered by Him whom Plato calls "The Great Geometer." There is still a third work of this ill-fated woman that deserves notice--namely, her _Astronomical Canon_, which dealt with the movements of the heavenly bodies. It is the general opinion that this was but a commentary on the tables of Ptolemy, in which event it is still possible that it may be found incorporated in the work of her father, Theon, on the same subject.