1. Combine the papaya, mango, sugar and lime juice in a heavy 3- to 4-quart enameled or stainless-steel saucepan. Bring to a boil over moderate heat, stirring constantly.
2. Reduce the heat to the lowest possible point and simmer uncovered for 30 to 40 minutes, or until most of the liquid has cooked away and the mixture is thick enough to hold its shape in a spoon.
3. As it begins to thicken, stir it frequently to prevent the jam from sticking to the bottom and sides of the pan.
4. Remove the pan from the heat. With a large spoon, ladle the jam immediately into hot sterilized canning jars or jelly glasses. Fill each jar to within ˝ inch of the top and seal it quickly and tightly with its ring and lid.
5. Fill each glass to within ˝ inch of the top, and at once pour a thin layer of hot paraffin over the surface of the jam, making sure it covers the jam completely and touches the glass all the way around.
6. Let the glasses rest until the paraffin cools and hardens; then cover them with metal lids.
