As our old rhyme from Barbados goes : "One of sour, two of sweet, three of strong, four of weak." Mix lime juice, sugar syrup, rum (I prefer the old stuff) and water in a pitcher or jug. Add a bit of grenadine for color, say a tablespoon or two to the batch. Chill. Serve on ice with a dash of bitters and nutmeg to taste.

Careful, now! This stuff is TASTY, STRONG, and might creep up on you before you know it! Cheers!