To every pound of blackberries allow two cups of sugar. Put the Berries in a porcelain-lined kettle, and cover them with the sugar and let them stand for two hours. Then set over a moderate fire and bring the mixture to a boiling point. Skim while boiling; pour immediately into cups and glasses, and cover tightly and place in a cool, dry place.
For Strawberry and Blackberry Jelly combined, allow equal parts of the fruits and proceed as above.