Sort, wash, and remove the stems from cherries.
Pit and coarsely chop the cherries; measure 1 1/2 cups.
Pit and chop the nectarines; measure 2 cups.
In 10-quart kettle or Dutch oven combine the chopped cherries and nectarines and lemon juice.
Add the powdered fruit pectin to the mixture; mix thoroughly.
Bring mixture to full rolling boil.
Stir in sugar.
Bring again to full rolling boil, stirring constantly.
Boil hard, uncovered, 1 minute.
Remove from heat; skim off foam with metal spoon.
Pour hot jam into hot, sterilized half-pint jars or glasses.