1In a saucepan, bring the apple cider, cranberry juice, cloves, allspice, cinnamon, sugar and orange to a boil over high heat. Cover, decrease heat tto low and simmer for 45 minutes, stirring occasionally. Strain out the spices and squeeze the liquid from the orange half into the juice and discard orange.
2Meanwhile, in a bowl, sprinkle gelatin over cold water and let sit 2 minutes. Add the juice mixture and stir until gelatin is dissolved.
3Stir in the rum. Refrigerate 90 minutes. Spoon into a 7-cup mold. Refrigerate until firm, about 4 hours.
4Unmold and garnish with the orange slices. Serve.