A person who, without any particular relation to a ship in distress, proffers useful service, and gives it as a volunteer adventurer, without any pre-existing covenant that connected him with the duty of employing himself for the preservation of that ship. The Clara, 23 Wall. 16, 23 L. Ed. 150; The Dumper, 129 Fed. 99, 63 C. C. A. 600; Central Stockyard Co. v. Mears, 89 App. Div. 452, 85 N. Y. Supp. 795.