The capital invested by corporations or citizens of other countries in such an enterprise must, in a great degree, look for protection to one or more of the great powers of the world. No European power can intervene for such protection without adopting measures on this continent which the United States would deem wholly inadmissible. If the protection of the United States is relied upon, the United States must exercise such control as will enable this country to protect its national interests and maintain the rights of those whose private capital is embarked in the work. An interoceanic canal across the American isthmus will essentially change the geographical relations between the Atlantic and Pacific coasts of the United States, and between the United States and the rest of the world. It will be the great ocean thoroughfare between our Atlantic and our Pacific shores, and virtually a part of the coast-line of the United States. Our merely commercial interest in it is greater than that of all other countries, while its relation to our power and prosperity as a nation, to our means of defense, our unity, peace, and safety, are matters of paramount concern to the people of the United States. No other great power would, under similar circumstances, fail to assert a rightful control over a work so closely and vitally affecting its interests and welfare. Without urging further the grounds of my opinion, I repeat, in conclusion, that it is the right and the duty of the United States to assert and maintain such supervision and authority over any interoceanic canal across the isthmus that connects North and South America as will protect our national interests. This I am quite sure will be found not only compatible with, but promotive of, the widest and most permanent advantage to commerce and civilization.[167] The message itself was accompanied by a report from the secretary of state, Mr. Evarts, in which he called attention to the mutual engagements entered into between the United States and Colombia by the treaty of 1846 in reference to a transit route across the isthmus and declared that the guarantee of the neutrality of the isthmus and of the sovereignty of Colombia over the same would be a very different thing when the isthmus should be opened to the interests and ambitions of the great commercial nations.[168]