Oranges and lemons wash, dry, cut in half, squeeze the juice, the bones are folded separately;
Zest cut into thin strips, add to the juice
In the original you'd have to tie bones in a knot of muslin cloth. In the absence of such cost gauze.
Pour all the chopped, pressed and a bundle of bones with water (2,800 l) and put on to cook - 2 hours.
That's what happened after two hours of cooking.
Warm the sugar in the oven on low heat for 20 minutes. Before you pour the sugar, remove the knot with the bones. Add sugar to the future marmalade after two hours. Mix thoroughly until the sugar dissolves, bring to a boil, cook over low heat for no more than 20 minutes.
Willing to test this: on a chilled saucer drop of marmalade, cool. If he winces at the touch of his finger, you're done.
Lay out in sterilized jars.