held that the service was ■one of towage, merely, and that the sum demanded was unreasonable and exorbitant; that, if the master had made such agreement under apprehension of the loss of his vessel, the court would not enforce it against him; but that in this case the brig was in no peril, and the tug was entitled to no more than a fair compensation, which, on the facts, was adjudged to be 200 milreas, or $224, without costs.