1. On day before canning, trim and discard thin dark-green outer skin from watermelon rind. Cut rind into 1-inch pieces to make about 14 cups. In very large bowl, dissolve salt in 6 cups water; add rind. (If necessary, add more water to cover rind.) Cover and refrigerate.
2. Next day, drain rind; rinse with running cold water; drain. In 10-quart Dutch oven over high heat, heat rind with water to cover to boiling. Reduce heat to low; simmer, uncovered, 30 minutes; drain. Tie cinnamon and cloves in double thickness of cheesecloth. In same Dutch oven, combine sugar, vinegar, 2 cups water, spice bag, and rind. Over high heat, heat to boiling. Reduce heat to low; cover; simmer 1 hour, stirring often. Meanwhile, prepare jars and caps for processing
3. Discard spice bag. Ladle simmering mixture into hot jars to 1/4 inch from top. Close jars as manufacturer directs. Process jars in boiling-water bath 10 minutes; cool jars and test for airtight seal