RESPONDING TO a near-constant flow of requests, George and Martha Washington sat for about two dozen portraits from 1789 to 1797, collected here in this elegantly illustrated volume. From miniatures executed on ivory for family and friends to a historical portrait that depicts Washington during the Revolution, the../images vary widely in treatment and setting. What they all reflect, Ellen Miles suggests, is the great need the new republic had for portraits of its first chief executive, often to stand in for Washington himself. In the portraits, Martha Washington is usually dressed plainly,...