His principal work, however, is the "Outlines of the Geology of England and Wales" (1822), being a second edition of the small work issued by William Phillips and written in co-operation with that author. The original contributions of Conybeare formed the principal portion of this edition, of which only Part 1, dealing with the Carboniferous and newer strata, was published. It affords evidence throughout of the extensive and accurate knowledge possessed by Conybeare; and it exercised a marked influence on the progress of geology in Britain.