Cut the lemons crosswise and remove seeds. Place the seeds in a cheesecloth bag, or tea infuser and set aside.

Quarter each lemon half and thinly slice the lemons into strips. Place the lemons, 4 cups of water and the bag/infuser of seeds in a nonreactive heavy pot and let mixture stand, covered, at room temperature 24 hours.

Once the mixture has sat for 24 hours, bring a boiling-water canner, 3/4 full with water, to simmer.

Wash jars and screw bands in hot soapy water; rinse with warm water. Pour boiling water over flat lids in saucepan off the heat. Let stand in hot water until ready to use. Drain well before filling.

When you are ready to make the marmalade, {after the lemon mixture has sat for 24 hours}, discard the lemon seeds and bring the lemon mixture to a boil over medium heat. Reduce the heat, and simmer, uncovered, until your mixture is reduced to about 4 cups {about 45 minutes to an hour}.

Stir in sugar and boil over moderate heat, stirring occasionally and skimming off any foam, until a teaspoon of mixture dropped on a cold plate gels, about 15 minutes.

Carefully ladle hot marmalade immediately into prepared jars, filling to within 1/4 inch of tops. Wipe jar rims and threads. Cover with two-piece lids and screw bands on.

Place jars on elevated rack in canner. Lower rack into canner. {Water must cover jars by 1 to 2 inches. Add boiling water, if necessary.} Cover; bring water to gentle boil. Process 5 min. Remove jars and place upright on towel to cool completely.

After jars cool, check seals by pressing middles of lids with finger. If lids spring back, lids are not sealed and refrigeration is necessary}.

Yields {5} 1/2 pints.