From 1922:
One pint of new milk, ½ oz. gelatine, sugar to sweeten, a strip or two of lemon rind. Soak the gelatine in the milk for a couple of hours. Strain off the milk, and put it on the fire to boil with the lemon rind, and sugar to taste. Let the milk almost reach boiling point. Take out the lemon and pour the milk on to the soaked gelatine, stirring well unlit the gelatine is dissolved. Strain into a basin or mould, and leave till firm. The addition of a tablespoonful or two of cream is a great improvement. Great care must be taken to get only the yellow part of the lemon rind, as the white part would give a very bitter taste to the jelly.