Moreover, there is no instance of the United States acquiescing in Great Britain's seizure of copper shipments. In every case in which it has been done vigorous representations have been made to the British Government, and the representatives of the United States have pressed for the release of the shipments. _(6) Submission without protest to interference with American trade to neutral countries in conditional and absolute contraband._ The fact that the commerce of the United States is interrupted by Great Britain is consequent upon the superiority of her navy on the high seas. History shows that whenever a country has possessed that superiority our trade has been interrupted and that few articles essential to the prosecution of the war have been allowed to reach its enemy from this country. The department's recent note to the British Government, which has been made public, in regard to detentions and seizures of American vessels and cargoes, is a complete answer to this complaint. Certain other complaints appear aimed at the loss of profit in trade, which must include at least in part trade in contraband with Germany, while other complaints demand the prohibition of trade in contraband, which appears to refer to trade with the Allies. _(7) Submission without protest to interruption of trade in conditional contraband consigned to private persons in Germany and Austria, thereby supporting the policy of Great Britain to cut off all supplies from Germany and Austria._ As no American vessel, so far as known, has attempted to carry conditional contraband to Germany or Austria-Hungary, no ground of complaint has arisen out of the seizure or condemnation by Great Britain of an American vessel with a belligerent destination. Until a case arises and the Government has taken action upon it, criticism is premature and unwarranted. The United States in its note of Dec. 28 to the British Government strongly contended for the principle of freedom of trade in articles of conditional contraband not destined to the belligerent's forces. _(8) Submission to British interference with trade in petroleum, rubber, leather, wool, &c._ Petrol and other petroleum products have been proclaimed by Great Britain as contraband of war. In view of the absolute necessity of such products to the use of submarines, aeroplanes, and motors, the United States Government has not yet reached the conclusion that they are improperly included in a list of contraband. Military operations today are largely a question of motive power through mechanical devices. It is therefore difficult to argue successfully against the inclusion of petroleum among the articles of contraband. As to the detention of cargoes of petroleum going to neutral countries, this Government has, thus far, successfully obtained the release in every case of detention or seizure which has been brought to its attention.