This section is from the book "Preserving And Pickling", by Mary M. Wright. Also available from Amazon: Preserving and Pickling: Two Hundred Recipes for Preserves, Jellies, Jams, Marmalades, Pickles, Relishes and Other Good Things.
All fruits should be carefully picked over and washed, and all the fuzz on peaches and quinces rubbed off. It is best to cook with their skins on fruits intended for jelly, as it will give the jelly a better flavor. Do not add water to currants or any of the juicy fruits, but set over a very slow fire until the juice begins to flow, then simmer slowly until the fruit is tender. Fill the fruit in a jelly bag and allow to drip into a vessel, but do not squeeze with the hands if you wish to have a nice clear jelly. After all the juice has dripped out, then one may place the fruit in a fruit press and squeeze out all the pulp possible. This can be made up into jams.