EXECUTIVE MANSION, May 31, 1870.

To the Senate of the United States:

I transmit to the Senate, for consideration with a view to its ratification, an additional article to the treaty of the 29th of November last, for the annexation of the Dominican Republic to the United States, stipulating for an extension of the time for exchanging the ratifications thereof, signed in this city on the 14th instant by the plenipotentiaries of the parties.

It was my intention to have also negotiated with the plenipotentiary of San Domingo amendments to the treaty of annexation to obviate objections which may be urged against the treaty as it is now worded; but on reflection I deem it better to submit to the Senate the propriety of their amending the treaty as follows:  First, to specify that the obligations of this Government shall not exceed the $1,500,000 stipulated in the treaty; secondly, to determine the manner of appointing the agents to receive and disburse the same; thirdly, to determine the class of creditors who shall take precedence in the settlement of their claims; and, finally, to insert such amendments as may suggest themselves to the minds of Senators to carry out in good faith the conditions of the treaty submitted to the Senate of the United States in January last, according to the spirit and intent of that treaty.  From the most reliable information I can obtain, the sum specified in the treaty will pay every just claim against the Republic of San Domingo and leave a balance sufficient to carry on a Territorial government until such time as new laws for providing a Territorial revenue can be enacted and put in force.

I feel an unusual anxiety for the ratification of this treaty, because I believe it will redound greatly to the glory of the two countries interested, to civilization, and to the extirpation of the institution of slavery.

The doctrine promulgated by President Monroe has been adhered to by all political parties, and I now deem it proper to assert the equally important principle that hereafter no territory on this continent shall be regarded as subject of transfer to a European power.

The Government of San Domingo has voluntarily sought this annexation.  It is a weak power, numbering probably less than 120,000 souls, and yet possessing one of the richest territories under the sun, capable of supporting a population of 10,000,000 people in luxury.  The people of San Domingo are not capable of maintaining themselves in their present condition, and must look for outside support.

They yearn for the protection of our free institutions and laws, our progress and civilization.  Shall we refuse them?

I have information which I believe reliable that a European power stands ready now to offer $2,000,000 for the possession of Samana Bay alone.  If refused by us, with what grace can we prevent a foreign power from attempting to secure the prize?