_The Mystery of Edwin Drood_ remains mysterious, but those who essay to conjecture the end of that unfinished story have at last the surety that its end, full worked out in all its details, had been in its author's mind before he set pen to paper.

His imagination was as diligent and as disciplined as his pen, Dickens' practice in this matter could not be better put than in his own words, when he describes himself as "in the first stage of a new book, which consists in going round and round the idea, as you see a bird in his cage go about and about his sugar before he touches it." That his plots are always highly elaborated is the fruit of this preliminary disciplined exercise of thought.

The method is familiar to many novelists now; Dickens was the first to put it into practice.

In the second place he made a new departure by his frankly admitted didacticism and by the skill with which in all but two or three of his books--_Bleak House_, perhaps, and _Little Dorrit_--he squared his purpose with his art.

Lastly he made the discovery which has made him immortal.