THE PRESIDENT AND WIFE OF AIDE ENJOY OPEN AIR CONCERT ON POTOMAC. WASHINGTON, D.C. JULY 12. THE PRESIDENT AND MRS. EDWIN M. WATSON, WIFE OF THE PRESIDENT'S AIDE, SITTING IN THE PRESIDENTIAL CAR LISTENING TO THE WASHINGTON SYMPHONY ORCHESTRA UNDER THE DIRECTION OF DR. HANS KINDLER AS THE ORCHESTRA PLAYED FROM ITS BARGE ON THE POTOMAC RIVER NEAR THE LINCOLN MEMORIAL. THE OPEN-AIR CONCERTS, WHICH BEGAN TONIGHT, WILL BE CONDUCTED TWICE A WEEK DURING THE SUMMER SEASON, AND WASHINGTONIANS TURN OUT TO SIT ON THE STEPS OR IN NEARBY BOATS TO LISTEN