IN BUT a few years one of the world's oldest Jewish communities will have disappeared. No more than 20 Jews are thought to still live in Egypt, compared to at least 80,000 before the second world war. Half a dozen live in Cairo—four of them in care homes. But Magda Haroun, a sprightly 65-year-old, wants to keep their memories alive. She has formed an association, Drop of Milk, dedicated to preserving Egypt's Jewish heritage. Of its 20 active members, she is the only Jew.