... Her most adoring pupil was Synesius, a bishop in the church who had died several years earlier. He addresses seven letters to Hypatia and refers to her in several more. Indeed, on his deathbed, he writes to her as "mother, sister, teacher, and withal benefactress, and whatsoever is honoured in name and deed" (Ep.16). She is "my most revered teacher" (Letter to Paeonius) and the one "who legitimately presides over the mysteries of philosophy" (Ep.137). And, in a letter written two years before her own death, he says "I account you as the only good thing that remains inviolate, along with virtue. You always have power, and long may you have it and make a good use of that power" (Ep.81). She taught Synesius how to make an astrolabe; he also requested a hydrometer from her, a device to measure the specific gravity of liquids. A philosopher, which is how Synesius repeatedly addresses her, Hypatia may have studied with Antoninus, who had prophesied the destruction of the Serapeum....
http://penelope.uchicago.edu/~grout/encyclopaedia_romana/greece/paganism/hypatia.htmlIt was written in 413, when Synesius was in great problems because he had a conflict with the governor Andronicus ...
To the Philosopher <Hypatia>
I salute you, and I beg of you to salute your most happy comrades for me, august Mistress. I have long been reproaching you that I am not deemed worthy of a letter, but now I know that I am despised by all of you for no wrongdoing on my part, but because I am unfortunate in many things, in as many as a man can be. If I could only have had letters from you and learnt how you were all faring -I am sure you are happy and enjoying good fortune- I should have been relieved, in that case, of half of my own trouble, in rejoicing at your happiness. But now your silence has been added to the sum of my sorrows. I have lost my children, my friends, and the goodwill of everyone. The greatest loss of all, however, is the absence of your divine spirit. I had hoped that this would always remain to me, to conquer both the caprices of fortune and the evil turns of fate.
http://www.livius.org/su-sz/synesius/synesius_letter_010.htmlWritten in 402, it is the world's first description of a hydrometer ...
To the Philosopher <Hypatia>
I am in such evil fortune that I need a hydroscope. See that one is cast in brass for me and put together. The instrument in question is a cylindrical tube, which has the shape of a flute and is about the same size. It has notches in a perpendicular line, by means of which we are able to test the weight of the waters. A cone forms a lid at one of the extremities, closely fitted to the tube. The cone and the tube have one base only. This is called the baryllium. Whenever you place the tube in water, it remains erect. You can then count the notches at your ease, and in this way ascertain the weight of the water.
http://www.livius.org/su-sz/synesius/synesius_letter_015.htmlTogether with Letter 10 (also to Hypatia, written in 413), this is the last piece of Synesius' correspondence ...
To the Philosopher <Hypatia>
I am dictating this letter to you from my bed, but may you receive it in good health, mother, sister, teacher, and withal benefactress, and whatsoever is honored in name and deed. For me bodily weakness has followed in the wake of mental sufferings. The remembrance of my departed children is consuming my forces, little by little. Only so long should Synesius have lived as he was still without experience of the evils of life. It is as if a torrent long pent up had bust upon me in full volume, and as if the sweetness of life had vanished. May I either cease to live, or cease to think of the tomb of my sons! But may you preserve your health and give my salutations to your happy comrades in turn, beginning with father Theotecnus and brother Athanasius, and so to all! And if any one has been added to these, so long as he is dear to you, I must owe him gratitude because he is dear to you, and to that man give my greetings as to my own dearest friend. If any of my affairs interests you, you do well, and if any of them does not so interest you, neither does it me.
http://www.livius.org/su-sz/synesius/synesius_letter_016.html