It is not difficult to imagine some youthful admirer of Carlyle giving a timid knock at the door, and then wishing that he had the courage to run away from the house before being ushered into the presence of the irascible Philosopher. Mr. Alma Tadema's knocker is forbidding enough in appearance, and holds out but little promise of the beauties of that wonderful house where the artist resides in St. John's Wood. No doubt it is, like everything else about his home, from a design by the great painter himself. [Illustration: THE DUKE OF DEVONSHIRE'S. (Piccadilly.)] The most beautiful knocker in this collection, if not the most beautiful in London, is that of the Duke of Devonshire, at No. 80, Piccadilly. It represents a head of classic contour set in a circular disc, chiselled with an exquisite border. Not a few among the Duke's guests have so far expressed their admiration of this work of art as to desire duplicates for themselves, but it is not known if any exist, it having been done by the Duke's own command from his own designs. It is to be wished that the Duke would follow up his artistic success in this particular by designing a wall for Devonshire House to replace the existing hideous structure. [Illustration: CHARLES DICKENS'. (17, Doughty Street.)] Dickens' door-knocker recalls the residence of the happy couple who removed to Doughty Street from Furnival's Inn shortly after their marriage. It was here that Charles Dickens the younger was born, and where the author of "Pickwick" first became on terms of friendship with many of the brilliant men of letters of his day. The knocker is held in its place by a fleur-de-lis of the same metal, and it was Serjeant Talfourd who humorously rallied Dickens on his supposed predilection for the French, who at that time were in the midst of preparing that series of more or less revolutionary movements which preceded the downfall of Louis Philippe and the ascendency of the third Napoleon. [Illustration: DR. JOHNSON'S. (Bolt Court, Fleet Street.)] But an older and more characteristic door-knocker may be found well within a mile of Doughty Street, still on the door of a house once inhabited by the great sage Dr. Samuel Johnson himself. Surely if any knocker is characteristic of its owner this one is. It represents a sturdy fist clenching a baton from which depends a bulky wreath of laurel fastened in the middle by a lion's head. The worthy doctor, as we are told by Boswell, carried no key, nor did he permit any member of his oddly-selected household to possess one. At all times and seasons the house in Bolt Court was inhabited, and unquestionably the burly knocker resounded in the ears of the inhabitants of the court often enough, and at unseemly hours, for the sage was not at all scrupulous as to what hours he kept, and many a time would talk irregularly on at the club until some of his neighbours had serious thoughts of rising. [Illustration: CRUIKSHANK'S. (Hampstead Road, N.W.)]