Pineapple Ginger Preserves

3 1/2 cups granulated sugar
2 (4 pound) pineapples, peeled and cut into 1/4-inch rings,
    cored, and chopped coarse (about 8 cups)
1/4 cup fresh gingerroot, peeled and finely chopped

In a heavy kettle combine the sugar and 2 cups water. Bring the mixture to a boil, stirring until the sugar is dissolved, and boil the syrup until it registers 220 degrees F on a candy thermometer. Stir in the pineapple and the gingerroot and simmer the mixture, uncovered, stirring to prevent scorching, for 1 hour, or until it registers 220 degrees F on a candy thermometer.

Remove the kettle from the heat and ladle the preserves into 5 sterilized 1/2-pint jars, filling the jars to within 1/4 inch of the tops. Wipe the rims with a dampened towel and seal the jars with the lids. Put the jars in a water bath canner or on a rack set in a deep kettle. Add enough hot water to the canner or kettle to cover the jars by 2 inches, and bring it to a boil. Process the jars, covered, for 10 minutes. Transfer them with tongs to a rack, and let them cool completely. Store the jars in a cool dark place.