Very recently it became known that on board of an English mail steamer, 'The Trent,' were two men, Messrs. SLIDELL and MASON, accredited agents from a portion of the United States which is in open and flagrant rebellion against a constituted government which has been recognized as such by every nation in the world. Those men, calling themselves ambassadors, and just as much entitled to that dignity or to official recognition as two agents from NENA SAHIB would have been during the revolt stirred up by that Hindoo, were taken by an officer of the United States government from the Trent, under the full impression by him that the seizure was in every sense legal. The British government regarded this arrest an outrage, and promptly responded by a demand for the restoration of Messrs. SLIDELL and MASON. Numerous 'indignation meetings' held in the great centres of English commerce and manufactures echoed this demand, which received a threatening form from the fact that great military and naval preparations, evidently aimed against the United States, were at once put under way. Was the seizure illegal? The vast amount of international law which has been brought to light on this subject, not merely in the press, but from the researches and pens of eminent jurists, led us to no severely definite conclusion. That an emissary is not a contraband of war as much as a musket or a soldier, appears preposterous, and offers a distinction which, as Mr. SEWARD observes, disappears before the spirit of the law, M. THOUVENEL to the contrary, notwithstanding. It was therefore in the mode of procedure in regard to the seizure of the emissaries that the trouble lay. According to law, the vessel, if carrying contraband of war, is liable to seizure. But if this assumed contraband be _men_, these may not be guilty, and are entitled to a trial. Still, as the law--or want of law--stands, the seizure of the vessel is the requisite step, the minor issue being practically regarded as the major; an anomaly not less striking than that which still prevails in certain courts, where, to recover damages for seduction, the defendant can only be mulcted in a penalty for the loss of time caused to his victim. It was not possible for Captain WILKES to seize the vessel, Great Britain declined to waive her claim to the execution of every jot and tittle of the letter of the law, and consequently the 'contrabands' were surrendered. The absurdity of involving two great nations in a war, on account of a legal paradox of this nature, requires no comment. The dry comment of General SCOTT, that the 'wrong' would have been none had it only been greater, recalls the absurd line in the old play:-- 'My wound is great because it is so small;' and the supplement,-- 'Then 'twould be greater were it none at all.'