Peel grapefruits moderately thin, like an apple, and discard yellow peel. Remove white rind in quarters right down to the meats, and set aside. Break up meats, remove core and seeds, and cut or crush pulp fine. Peel of orange skin in quarters down to meat and set aside. Break up orange pulp, remove seeds, and combine orange and grapefruit pulps and juice in medium- sized saucepan. Put grapefruit whites through food chopper, or chop fine by hand, and boil slowly with 1 1/2 cups water in covered saucepan for 10 minutes. Strain all liquor possible from cooked whites, through a sieve, into saucepan with combined pulps. Repeat cooking and straining with fresh portion of 1 1/2 cups water and discard cooked whites. Simmer pulp and drained liquor in covered pan 45 minutes. Boil orange skins hard with 4 cups water in covered pan 30 minutes, to make them tender. Drain off and discard water. With sharpened spoon scrape out and discard all the white part right down to yellow rind. Then with a very sharp knife shred yellow rinds just as thin as possible in shreds about 1 inch long. Mix shredded rinds with cooked pulp. Measure 4 level cups of this mixture into large saucepan, adding, if necessary, enough water to the fourth cup to make it level full. Add sugar and mix well. Stir mixture hard and constantly and bring to a vigorous boil over the hottest fire. Boil hard 3 minutes with continual stirring. Remove from fire and add pectin, stirring it in well. Then let stand five minutes only, by the clock, with occasional stirring to cool slightly and pour quickly.