On two ounces and a half of the finest isinglass, pour a full but an exact pint of spring water; press down the isinglass and turn it over until the whole is well moistened; then place it over a gentle fire and let it dissolve gradually; remove the scum after it has simmered for two or three minutes, then pour it out, and set it aside to cool. In another pint of spring water boil a pound of highly refined sugar for five or six minutes; turn this syrup into a bowl, and when it is only just warm, throw into it the very thinly pared rinds of two fine lemons, of two Seville oranges, and of two China oranges, with the juice of five China, and of two Seville oranges, and of three lemons. When this mixture is cold, but not beginning to thicken, mix it well with the liquid isinglass, and strain it through a fine lawn sieve, or through a square or muslin folded in four; pour it into moulds which have been laid in cold water, and when wanted for the table, loosen it from them by wrapping about them, closely, a cloth which has been dipped into boiling water, and by passing a knife round the edges.
Nothing can be more refined and delicate in flavour than the above; but the appearance of the jelly may be improved by clarifying the isinglass, and its colour by boiling the fruit-rinds in the syrup for three or four minutes, and by leaving them in it until it is strained. The oranges and lemons, if good, will yield from two-thirds to three-quarters of a pint of juice, and the quantity of jelly will be sufficient to fill one large high mould, or two smaller ones which contain about a pint and a quarter each.
When the isinglass is clarified, allow half an ounce more of it; take about a teaspoonful of the white of a fresh egg, beat it a little, add the pint of cold water to it, whisk them together for a minute or two, and then pour them on the isinglass; stir it occasionally as it is heating, but not after the head of scum is formed: boil it gently for two or three minutes, skim, and strain it. The oranges and lemons should be dipped into fresh water and wiped dry before they are pared; and should a muslin strainer (that is to say, a large square of common clean muslin) be used for the jelly, it should be laid after being washed in the usual manner into plenty of hot water, and then into cold, and be well rinsed in, and wrung from each.