commerce. Small vessels employed in loading and unloading larger vessels. 2. The owners of lighters are liable, like other common carriers for hire; it is a term of the contract on the part of the carrier or lighterman, implied by law, that his vessel is tight and fit for the purpose or employments for which he offers and holds it forth to the public; it is the immediate foundation and substratum of the contract that it is so: the law presumes a promise to that effect on the part of the carrier without actual proof, and every principle of sound policy and public convenience requires it should be so.