Gather the walnuts when well grown, but still soft enough to be pierced through with a needle. Run a heavy needle through them several times and place them in strong brine, using as much salt as the water will absorb. Let them remain in brine for a week or ten days, and change the brine every other day; then drain the nuts and expose them to the air until they have turned black. Pack them in jars and cover them with boiling hot vinegar prepared as follows: To a gallon of vinegar add an ounce each of ginger root, mace, allspice, and cloves, and two ounces of peppercorns; boil them together for ten minutes and strain over the nuts. Let them stand a month before using.