Olympias used to write very frequently to Alexander, and in these letters she would criticise and discuss his proceedings, and make comments upon the characters and actions of his generals. Alexander kept these letters very secret, never showing them to any one. One day, however, when he was reading one of these letters, Hephæstion, the personal friend and companion who has been already several times mentioned, came up, half playfully, and began to look over his shoulder. Alexander went on, allowing him to read, and then, when the letter was finished he took the signet ring from his finger and pressed it upon Hephæstion's lips, a signal for silence and secrecy.