Use thick pieces of large fish for boiling, or if small fish are used they may be boiled whole. Add salt and vinegar to water in proportion of 1 tablespoonful of salt and two of vinegar to three quarts of water. Use enough water to cover the fish. Wrap the fish in cheesecloth to prevent breaking apart, and plunge into boiling water. Do not let the water boil after fish is in. The fish is done when the flesh leaves the bone or when the flesh flakes apart easily. The usual time for a thick piece is 30-40 minutes.