In completing this series of pictures, I wish emphatically to insist on the imperfection of the sketches which I have been able to present, and which are less, in comparison with the grand march of the creative work, even as now imperfectly known to science, then the roughest pencilling of a child when compared with a finished picture. If they have any popular value, it will be in presenting such a broad general view of a great subject as may induce further study to fill up the details. If they have any scientific value, it will be in removing the minds of British students for a little from the too exclusive study of their own limited marginal area, which has been to them too much the "celestial empire" around which all other countries must be arranged, and in divesting the subject of the special colouring given to it by certain prominent cliques and parties. Geology as a science is at present in a peculiar and somewhat exceptional state. Under the influence of a few men of commanding genius belonging to the generation now passing away, it has made so gigantic conquests that its armies have broken up into bands of specialists, little better then scientific banditti, liable to be beaten in detail, and prone to commit outrages on common sense and good taste, which bring their otherwise good cause into disrepute. The leaders of these bands are, many of them, good soldiers, but few of them fitted to be general officers, and none of them able to reunite our scattered detachments. We need larger minds, of broader culture and wider sympathies, to organise and rule the lands which we have subdued, and to lead on to further conquests.