Melon Pickles

Three pounds melon, cover with vinegar, let stand overnight and next morning add 2lb. of sliced onion, 2 cupfuls brown or white sugar, 1 dessertspoonful of salt, 1 teaspoonful of mixed spice, ½ teaspoonful of cayenne pepper; boil for an hour or longer, then mix together 1 teaspoonful of mustard; 1 teaspoonful turmeric, 1 teaspoonful flour, with cold vinegar; add to boiled ingredients and let boil a little longer.