To twelve pounds or six quarts of berries allow nine pounds
of sugar, that is, in the proportion of a pound of fruit to three quarters of a pound of sugar. Put the berries in your preserving kettle, crushing them with the bark of a wooden spoon, and let them come slowly to a boil. To avoid the risk of scorching it is well to put a thick inverted plate in the bottom of the kettle. Cook steadily half an hour after they reach the boil, stirring them often, and then turn in the sugar. Cook for twenty minutes after this goes in, have your jars ready, and put the jam into them while boiling hot. Roll each jar in boiling water before filling it or stand it on a wet cloth or put a spoon in it. Any of these expedients is a protection against breakage.
If the berries are not exceptionally dry there will probably be more juice than the jam needs, and this you can dip out and put up separately. It may be converted into jelly or into blackberry vinegar or shrub, or canned to use for flavoring for pudding sauces in winter.
Raspberry Jam: Put up either black or red raspberries by this same recipe, which is also good for blueberry jam.