Pick prickly pears with leather gloves on your hands. Take off spines. Rinse the fruit and place in kettle, adding enough water to cover. Boil until quite tender, squeeze through jelly bag or jelly press. To every 2 1/2 cups of juice add 1 (1 3/4 oz.) package powdered pectin and boil for a couple minutes. Then add 3 tablespoons lemon juice and 3 1/2 cups sugar. Stir often and boil hard for 5 minutes. Pour in jelly glass and seal with paraffin.