to retract, but much to carry forward, and which has been carried forward, as I trust one day to show," was an expression used by him in speaking of these papers. Whether the conflict between his earlier and later views be real or apparent, the editors have not felt themselves authorised to attempt any correction or amplification; these essays are left as they were originally written, with omission of one or two pages quite irrelevant to the purport of the argument. They believe this plan to be in accordance with the spirit which animated Mr Ferrier's own researches: for he was far too fearless and faithful a follower of truth to have hesitated for a moment to throw aside an opinion once held, if shown to be fallacious, or to doubt that from the collision of imperfectly discerned truths a spark might be struck out that would light to further insight. Those to whom the system of this philosopher, when brought nearer to maturity, presents matter of interest, will thus have the best assistance that can be supplied towards tracing its growth through successive stages; they are asked in return nothing but what every labour of thought has a right to claim from a reader, to understand each combination of ideas, where there can be room for doubt, according to their best admissible meaning.
Many may be of opinion that some regions into which the ocean of philosophic discovery spreads, have not been tracked with sufficient diligence by this explorer; such comparative incompleteness may
