In Belden v. Chase, 150 U.S. 699, 14 Sup. Ct. 264 (1893), it was said: 'It is a settled rule in this court that when a vessel has committed a positive breach of statute she must show not only that probably her fault did not contribute to the disaster, but that it could not have done so. Obedience to the rule is not a fault, even if a different course would have prevented the collision. Masters are bound to obey the rules and entitled to rely on the assumption that they will be obeyed, and should not be encouraged to treat the exceptions as subjects of solicitude rather than the rules.'