1. Cut watermelon in half; remove flesh and seeds. Using a metal spoon, scrape rind to remove all traces of pink. Cut rind crosswise in 1-inch-wide strips. Using a vegetable peeler or a small sharp knife, peel the green skin from the rind. Cut away any bruises or bad spots. Cut rind into 2-inch lengths.

2. In a large nonreactive bowl, combine salt and 1 gallon cold water. Add rind; let soak in brine overnight. Rinse rind 2 or 3 times in fresh cold water, and drain well.

3. Combine sugar and vinegar in a large nonreactive pot, and heat until sugar is dissolved. Fold an 8-by-16-inch piece of cheesecloth in half to make a square; rinse, and squeeze dry. Place ginger, spices, and lemon on the cheesecloth. Tie cloth closed with one end of a 12-inch piece of kitchen twine. Tie a loop in the other end, and slip it over the handle of a wooden spoon. Suspend spice bag in the vinegar syrup by placing the spoon across the top of the pot. Add rind to the pot, and return to a boil. Reduce heat, simmer for 30 minutes, and let sit overnight. Discard spice bag.

4. Wash seven 1-pint canning jars, lids, and screw bands with hot, soapy water, and rinse well. Place jars upright on a wire rack in the bottom of a large pot. Fill pot with hot water until jars are submerged by 1 to 2 inches, and bring to a boil. Boil for 15 minutes. Turn off heat, leaving jars in water. Sterilize lids according to manufacturer's instructions.

5. Using stainless-steel tongs, remove jars from water, and place on a layer of clean towels. With a slotted spoon, transfer rind to jars, leaving 3/4 inch of space beneath the rim. Return syrup to a boil. Pour hot syrup over rind, covering it by 1/4 inch and leaving 1/2 inch of space beneath the rim. Slide a clean plastic chopstick or wooden skewer along inside of each jar to release any air bubbles. Wipe mouth of jar with a clean, damp cloth. Place hot lid on jar; turn screw band firmly without forcing.

6. Place a wire rack in the bottom of a large pot, and fill partway with hot water. Using a jar lifter, place jars upright on rack. Add enough hot water to cover by 2 inches, and bring to a boil. Boil for 10 minutes. Remove jars from water bath; let stand on clean dish towels for 24 hours. Check cool jars for the slight indentation in the lids that indicates a vacuum seal. Jars that do not seal properly or that leak during processing should be stored in the refrigerator and pickles consumed within a week. Allow sealed pickles to mellow in a cool, dry place for 2 to 3 weeks. Store opened jars in the refrigerator.