These cases show that for the purposes of liability the passive instrument of the harm does not become one with the actively responsible vessel by being attached to it. If this were a proceeding in rem it may be assumed that the car float and disabled tug would escape, and none the less that they were lashed to the Intrepid, and so were more helplessly under its control than in the ordinary case of a tow.

It is said, however, that when you come to limiting liability, the foregoing authorities are not controlling,—that the object of the statute is "to limit the liability of vessel owners to their interest in the adventure," and that the same reason that requires the surrender of boats and apparel requires the surrender of the other instrumentalities by means of which the tug was rendering the services for which it was paid. It can make no difference, it is argued, whether the cargo is carried in the hold of the tug or is towed in another vessel. But that is the question, and it is not answered by putting it. The respondent answers the argument with the suggestion that, if sound, it applies a different rule in actions in personam from that which, as we have said, governs suits in rem. Without dwelling upon that, we are of opinion that the statute does not warrant the distinction for which the petitioner contends.

In the case of Sturgis v. Boyer, 24 How. 110, the ship Wisconsin, which was being towed by the tug Hector, collided with the lighter Republic in New York harbor. The owners of the lighter libeled both the tug and the tow. The owner of the tug filed an answer, setting up that the tug was merely the motive-power to move the ship to the pier, that the tug and her crew were subject to and obeyed the orders of the master and other officers in charge of the ship, and prayed that in case the libellants should recover any sum against the ship and tug, that he, the owner of the tug, might have decree over against the ship. The owners of the ship admitted that she had a master and a full crew on board, but alleged that they were all under the direction and control of the master and officers of the tug. The Court was clearly of opinion that a case of negligence was made out by the owners of the lighter, and the only question in doubt was as to the relative responsibility of the tug and vessel in tow.

Cases arise, undoubtedly, when both the tow and the tug are jointly liable for the consequences of a collision; as when those in charge of the respective vessels jointly participate in their control and management, and the master or crew of both vessels are either deficient in skill, omit to take due care, or are guilty of negligence in their navigation. Other cases may well be imagined when the tow alone would be responsible; as when the tug is employed by the master or owners of the tow as the mere motive power to propel their vessels from one point to another, and both vessels are exclusively under the control, direction and management of the master and crew of the tow. Fault in that state of the case cannot be imputed to the tug, provided she was properly equipped and seaworthy for the business in which she was engaged; and if she was the property of third persons, her owners cannot be held responsible for the want of skill, negligence or mismanagement of the master and crew of the other vessel, for the reason that they are not the agents of the owners of the tug, and her owners in the case supposed do not sustain towards those entrusted with the navigation of the vessel the relation of the principal. But whenever the tug, under the charge of her own master and crew, and in the usual and ordinary course of such an employment, undertakes to transport another vessel, which, for the time being, has neither her master nor crew on board, from one point to another, over waters where such accessory motive power is necessary or usually employed, she must be held responsible for the proper navigation of both vessels; and third persons suffering damage through the fault of those in charge of the vessels must, under such circumstances, look to the tug, her master or owners, for the recompense which they are entitled to claim for any injuries that vessels or cargo may receive by such means. Assuming that the tug is a suitable vessel, properly manned and equipped for the undertaking, so that no degree of negligence can attach to the owners of the tow, on the ground that the motive power employed by them was in an unseaworthy condition, and the tow, under the circumstances supposed, is no more responsible for the consequences of a collision than so much freight; and it is not perceived that it can make any difference in that behalf, that a part, or even the whole of the officers and crew of the tow are on board, provided it clearly appears that the tug was a seaworthy vessel, properly manned and equipped for the enterprise, and from the nature of the undertaking, and the usual course of conducting it, the master and crew of the tow were not expected to participate in the navigation of the vessel, and were not guilty of any negligence or omission of duty by refraining from such participation.

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Unless the owner and the person or persons in charge of the vessel in some way sustain towards each other the relation of principal and agent, the injured party cannot have his remedy against the colliding vessel. By employing a tug to transport their vessel from one point to another, the owners of the tow do not necessarily constitute the master and crew of the tug their agents in performing the service. They neither appoint the master of the tug, or ship the crew; nor can they displace either one or the other. Their contract for the service, even though it was negotiated with the master, is, in legal contemplation, made with the owners of the vessel, and the master of the tug, notwithstanding the contract was negotiated with him, continues to be the agent of the owners of his own vessel, and they are responsible for his acts in her navigation.

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Whether the party charged ought to be held liable, is made to depend, in all cases of this description, upon his relation to the wrongdoer. If the wrongful act was done by himself, or was occasioned by his negligence, of course he is liable, and he is equally so, if it was done by one towards whom he bore relation of principal; but liability ceases where the relation itself entirely ceases to exist, unless the wrongful act was performed or occasioned by the party charged.

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Applying these principles to the present case, it is obvious what the result must be. Without repeating the testimony, it will be sufficient to say, that it clearly appears in this case that those in charge of the steam tug had the exclusive control, direction and management of both vessels, and there is not a word of proof in the record, either that the tug was not a suitable vessel to perform the service for which she was employed, or that any one belonging to the ship either participated in the navigation, or was guilty of any degree of negligence whatever in the premises.