Wipe apples, remove stem and blossom ends, and cut in quarters. Put in a granite or porcelain-lined preserving kettle, and add cold water to come nearly to top of apples. Cover, and cook slowly until apples are soft; mash, and drain through a coarse sieve. Avoid squeezing apples, which makes jelly cloudy. Then allow juice to drip through a double thickness of cheese cloth or a jelly bag. Boil twenty minutes, and add an equal quantity of heated sugar; boil five minutes, skim, and turn in glasses. Put in a sunny window, and let stand twenty-four hours. Cover, and keep in a cool, dry place. Porter apples make a delicious flavored jelly. If apples are pared, a much lighter jelly may be made. Gravenstein apples make a very spicy jelly.