[Footnote 253: The microscopic structure of this wood was briefly described by Witham (_Fossil Vegetables_, p. 37), and two magnified representations were given to show its coniferous character. Lindley and Hutton further described it in their "Fossil Flora," naming it _Pinites eiggensis_, and regarding it as belonging to the Oolitic series of the Hebrides--an inference founded perhaps on the erroneous statement of Witham to that effect. William Nicol corrected that statement by showing that the wood-fragments occurred, not among the "lias rocks," but "among the debris of the pitchstone" (_Edin. New Phil. Journal_, xviii. p. 154). Hay Cunningham, in the paper already cited, states that the fossil wood really lies in the pitchstone itself! The actual position of the wood, however, in the breccia and conglomerates underlying the pitchstone is beyond all dispute. I have myself dug it out of the bed. The geological horizon assigned to this conifer, on account of its supposed occurrence among Oolitic rocks, being founded on error, no greater weight can be attached to the identification of the plant with an Oolitic species. Our knowledge of the specific varieties of the microscopic structure of ancient vegetation is hardly precise enough to warrant us in definitely fixing the horizon of a plant merely from the examination of the minute texture of a fragment of its wood. From the internal organization of the Eigg pine, there is no evidence that the fossil is of Jurassic age. From the position of the wood above the dolerites and underneath the pitchstone of the Scuir it is absolutely certain that the plant is not of Jurassic but of Tertiary date.] It is at the extreme north-western extremity of the pitchstone ridge, however, that the most remarkable exposure of this intercalated detrital band is now to be seen. Sweeping along the crest of the plateau the ridge reaches the edge of the great precipice of Bideann Boidheach, by which its end is truncated, so as to lay open a section of the gravelly deposit along which the pitchstone flowed.