Having procured berries that are fully ripe, put them into a large
vessel of wood or stone, with a cock in it, and pour upon them as
much boiling water as will cover them. As soon as the heat will
permit the hand to be put into the vessel, bruise them well till all
the berries are broken. Then let them stand covered till the berries
begin to rise towards the top, which they usually do in three or four
days. Then draw off the clear into another vessel, and add to every
ten quarts of this liquor, a pound of sugar. Stir it well and let it
stand to work a week or ten days, in another vessel like the first.
Then draw it off at the cock through a jelly-bag into a large vessel.
Take four ounces of isinglass, and lay it to steep twelve hours in a
pint of white wine. The next morning, boil it upon a slow fire till
it is all dissolved. Then take a gallon of blackberry-juice, put in
the dissolved isinglass, give them a boil together, and pour all into
the vessel. Let it stand a few days to purge and settle, then draw it
off, and keep it in a cool place.