Preheat the oven to 175F. Butter and flour a large baking sheet. In the bowl of an electric mixer beat the egg whites to the soft peak stage, then beat in half the sugar. Continue beating until stiff, then fold in the remaining sugar, flour, and vanilla extract. Fill a pastry bag fitted with a 1/2-inch plain nozzle with the meringue and pipe into small 1-inch mounds on the baking sheet. Bake for 1 hour. Remove the meringues from the baking sheet carefully and cool on a wire rack.
