Some of these dominant elements in our surroundings remain permanently with little or no appreciable change. The mountains and the plains are now essentially what they were in the infancy of man, though their mantle of vegetation may have been greatly altered. In other cases, geological processes are continually at work, effecting changes which, though individually of small account, become important in the course of centuries by constant repetition. Thus on some parts of our coast-line there has been a great destruction of land, in others the land has gained on the sea. But man himself has become a geological agent, and has in that capacity greatly modified the surface of many of the countries which he has inhabited. The progress of agriculture has led to the draining of mosses, the felling of forests and the transformation of heaths and wastes into arable land. The increase of sheep and cattle has been the means of clothing the hills with pasture, in place of their former rough herbage and copsewood. And man himself becomes involved in the consequences of the changes which he sets in motion. This subject may obviously be discussed independently either from the scientific or from the historical side. Any investigation which deals with the changes that have taken place in the outward aspect of a country since man first set foot upon its surface, and with the sources of information regarding them, must obviously appeal strongly to the lover of science, inasmuch as it brings before him the evidence for various kinds of geological process, the actual operation and rate of progress of which he may thereby be enabled to watch and determine. It may thus be made to throw light upon one of the vexed problems of science--the value of time in geological inquiry. But it is of the relations of such an investigation to human history that I would first more particularly speak. Such inquiries seem to me eminently calculated to engage the sympathies and even the active co-operation of literary students. There can be no doubt that the advancement of our knowledge of the mutations of the land since the beginning of history must depend largely upon help from the study of historical documents.