To eighteen ripe oranges, use six pounds best white sugar. Grate the peel from four oranges; reserve for marmalade. (The rinds of the remainder will not be used). Pare the fruit, removing the white skin as well as the yellow; slice the oranges; remove all seeds. Put the fruit and grated peel into a preserving kettle; boil until reduced to a smooth mass; rub quickly through a colander; stir in the sugar; return to the stove; boil fast, stirring constantly, one-half hour, or until thick. Put in glasses, or jars; cover closely when cold.