Wash pears and very carefully rub off the spines with a thick cloth.
Cut pears into halves and put in kettle.
Add water and cook until fruit is soft and almost pulpy.
Put in jelly cloth or bag and squeeze out juice.
Measure 4 cups into a very large saucepan.
Stir in lemon juice and sugar.
Put over high heat and bring to a boil, stirring constantly.
At once stir in pectin.
Then bring to a full rolling boil and boil hard for 1 minute, stirring constantly.
Remove from heat, skim off foam with metal spoon, and pour quickly into hot sterilized jars; seal.