Libanius, Orat. Parent. c. x. p. 233, 234. Gallus had some reason to suspect the secret apostasy of his brother; and in a letter, which may be received as genuine, he exhorts Julian to adhere to the religion of their ancestors; an argument which, as it should seem, was not yet perfectly ripe. See Julian. Op. p. 454 [ed. Spanheim, Lips. 1696], and Hist. de Jovien, tom. ii. p. 141.