The following speech[1] was delivered at the invitation of the New York Young Men’s Republican Union, at Cooper Institute, on the 10th of September, 1863. The announcement that Mr. Sumner had consented to address the citizens of New York on a subject so momentous attracted an audience numbering not less than three thousand persons, among whom were most of the acknowledged representatives of the intelligence, wealth, and influence of the metropolis. Long before the hour appointed for the delivery of the speech, the entrance-doors were besieged by an impatient and anxious crowd, who, as soon as the gates were opened, filled the seats, aisles, lobbies, and platform of the vast hall, leaving at least an equal number to return home, unable to gain an entrance to the building. Of the following named gentlemen, who were invited to occupy seats upon the platform, a majority were present, while in the auditorium were hundreds of equally prominent citizens, who preferred to retain seats near the ladies whom they had escorted to the meeting. Francis Lieber, LL.D., George Bancroft, Major-General Dix, Horace Greeley, George Griswold, John E. Williams, W. W. DeForest, Cornelius Vanderbilt, Abram Wakeman, Rev. Dr. Tyng, Cyrus W. Field, Alexander T. Stewart, Horace Webster, LL.D., Joseph Lawrence, John A. Stevens, Pelatiah Perit, James A. Hamilton, H. B. Claflin, T. L. Thornell, Colonel William Borden, William Goodell, Rev. Dr. Thompson, Rev. Dr. Gillette, William Cullen Bryant, Major-General Fremont, A. A. Low, John Jay, Henry Grinnell, James Gallatin, Cephas Brainerd, William B. Astor, William H. Aspinwall, Oliver Johnson, W. M. Evarts, William Curtis Noyes, Rev. Dr. Hitchcock, Shepherd Knapp, William H. Webb, James W. Gerard, Anson Livingston, Frank W. Ballard, Isaac H. Bailey, George B. Lincoln, General Harvey Brown, Rev. Dr. Shedd, Rev. Dr. Durbin, Peter Cooper, Major-General Doubleday, Charles H. Marshall, Marshall O. Roberts, Judge Bradford, Charles H. Russell, E. Delafield Smith, Hamilton Fish, Robert B. Minturn, Rev. Dr. Cheever, F. B. Cutting, Charles King, LL.D., Rev. Dr. Ferris, Ex-Governor King, George Folsom, Samuel B. Ruggles, S. B. Chittenden, Charles T. Rodgers, Mark Hoyt, Lewis Tappan, Rev. Dr. Storrs, Rev. Dr. Adams, Rev. Dr. Vinton, Daniel Drew, Francis Hall, George William Curtis, Judge Edmonds, Rev. Dr. Asa D. Smith, Truman Smith, William A. Hall, Prosper M. Wetmore, B. F. Manierre, George P. Putnam, E. C. Johnson, Rev. Dr. Osgood, Elliott C. Cowdin, Rev. T. Ralston Smith, J. S. Schultz, M. Armstrong, Jr., D. A. Hawkins, Edgar Ketchum, Joseph Hoxie, Rev. Dr. Bellows, General S. C. Pomeroy, James McKaye, George F. Butman, David Dudley Field.