Place the sliced pears and sugar in a large preserving kettle.
Peel the zest off the lemons, and sliver finely.
Juice the lemons.
Add these ingredients and the ginger to the pears.
Stir well, cover and leave overnight.
The next day, uncover, bring to the boil, reduce heat and stirring frequently, simmer gently 40-45 minutes or until the marmalade is thick and the fruit transparent.
Pour into hot sterilized jars.
Seal with melted paraffin wax.