But the works which he published represent imperfectly the labour spent on the undertaking. Besides these there remains a vast amount of unused or rejected work, which shows how it was thought out, rearranged, tried first in one fashion and then in another, recast, developed. Separate chapters, introductions, "experimental essays and discarded beginnings," treatises with picturesque and imaginative titles, succeeded one another in that busy work-shop; and these first drafts and tentative essays have in them some of the freshest and most felicitous forms of his thoughts. At one time his enterprise, connecting itself with his own life and mission, rose before his imagination and kindled his feelings, and embodied itself in the lofty and stately "Proem" already quoted. His quick and brilliant imagination saw shadows and figures of his ideas in the ancient mythology, which he worked out with curious ingenuity and often much poetry in his _Wisdom of the Ancients_. Towards the end of his life he began to embody his thoughts and plans in a philosophical tale, which he did not finish--the _New Atlantis_--a charming example of his graceful fancy and of his power of easy and natural story-telling. Between the _Advancement_ and the _Novum Organum_ (1605-20) much underground work had been done. "He had finally (about 1607) settled the plan of the _Great Instauration_, and began to call it by that name." The plan, first in three or four divisions, had been finally digested into six. Vague outlines had become definite and clear. Distinct portions had been worked out. Various modes of treatment had been tried, abandoned, modified. Prefaces were written to give the sketch and purpose of chapters not yet composed. The _Novum Organum_ had been written and rewritten twelve times over. Bacon kept his papers, and we can trace in the unused portion of those left behind him much of the progress of his work, and the shapes which much of it went through. The _Advancement_ itself is the filling-out and perfecting of what is found in germ, meagre and rudimentary, in a _Discourse in Praise of Knowledge_, written in the days of Elizabeth, and in some Latin chapters of an early date, the _Cogitationes de Scientia Humana_, on the limits and use of knowledge, and on the relation of natural history to natural philosophy. These early essays, with much of the same characteristic illustration, and many of the favourite images and maxims and texts and phrases, which continue to appear in his writings to the end, contain the thoughts of a man long accustomed to meditate and to see his way on the new aspects of knowledge opening upon him. And before the _Advancement_ he had already tried his hand on a work intended to be in two books, which Mr. Ellis describes as a "great work on the Interpretation of Nature," the "earliest type of the _Instauratio_," and which Bacon called by the enigmatical name of _Valerius Terminus_. In