MRS. MACKAY’S TRIUMPH.A Flank Movement That Captured the Prince of Wales.New York World’s London Cable : Mrs. Mackay took a flyer this week, which has become the prevailing topic of conversation in the social world, and which has created a tremendous sensation among the American set. Last season there was a wild attempt made to crowd Mrs. Mackay into the background, and this year the movement was beginning to develop into open hostility. For some time past the rumor has been current, and has even crept into print, that the Prince of Wales and ail the Marlborough House set intended to give Mrs. Mackay the cut direct.A few days ago one of the shining lights of the American colony was riding with Mrs. Mackay in her carriage, and felt it incumbent upon her to tell Mrs. Mackay as gently as possible of the intended royal snub. Mrs. Mackay promptly responded by giving this lady an invitation to come to her house after dinner on Wednesday evening last to meet the Prince of Wales, who wa9 going to dine with her on that night. Mrs. Mackay thoroughly understood the true social significance of her bold stroke to assert her position in the London world, and her dinner to the Prince on Wednesday night was a marvel. The guest of the evening to meet the Prince, so far as Americans were concerned, was Mrs. Edward Jaflray. who sat near him, and with whom H. R. H. was very much pleased. Lady Playfair and Lady Randolph Churchill were also present. The house was a perfect paradise of flowers. Table decorations were of pale yellow roses and orchids. The staircase from the entrance hall to the ballroom flight was banked with the choicest exotics. The ballroom was hung with pink roses and smilax, and in each window were gilded stands holding immense bunches of pink roses and white orchids tied with long ribbons. Mrs. Mackay’s dress was brought from Paris for the occasion. It was of white satin, embroidered with white lilies of the valley and leaves in their natural colors. She carried a bouquet of the same flowers. Her ornaments were pearls and diamonds. Lady Randolph Churchill was superbly dressed in pale yellow’. After dinner Mrs. Mackay gave a concert, and sent over to Paris for distinguished artists from the theatres and operas there to take part in it.A short piece, performed by members of the Paris Opera Comique, cost alone nearly $5,000. An American girl, Mercedes Leigh, was permitted to give some recitations.Among the Americans invited to meet the Prince at the concert were Mrs. Ronalds, Mrs. Jerome, Mr. and Mrs. Morton Frewen, Mrs. Cavendish Bentinck, Mrs. Horne Payne, Miss Balch, Mr. George W. Smalley and Mr. Albert Van Wagner. Sir Julian and Lady Paunce-fote were there too. The Prince's 6upper was served in a room apart from that of the other guests, and he was allowed to invite his own party. He paid Lady Randolph the compliment of sending for her from the general supper-room and of asking her to sup with him. Mrs. Mackay is not going to be socially crushed this season at least.G