Add the raisins to the hot milk. Mix 1 cup cold milk with the cornmeal, then stir into the hot milk. Heat very slowly, stirring constantly, for about 10 to 15 minutes or until the mixture thickens. Mix in the molasses, salt, sugar, ginger, nutmeg, & butter. Pour into a buttered 2-quart casserole. Then pour the remaining 1/2 cup cold milk into the center of the pudding. Set dish in a pan of cold water, & bake in a slow oven, 300 F., for 2 1/2 hours. Let cool for 3 to 4 hours before serving.