Sauce of Cherries

Remove the pits from ½ pound ripe cherries; put the stones into a mortar and pound them fine; put them, with the cherries, 1 pint water and a piece of cinnamon, in a saucepan; add ¾ cup sugar and boil slowly ½ hour; strain and thicken the sauce with 2 teaspoonfuls cornstarch; boil a minute, add ½ cup claret and serve.