31 CHAP. IV. On the general Disposition of the Surface of the Globe. lo consider, in all its details, the subject which forms the title of this Chapter, would be to trespass on the province of Physical Geography. But this department of Geographical science is in so many points implicated with geology, that it is impossible to avoid bestowing on it some consideration, although it cannot here be allowed a large space. If it is the business of the Geographer to trace the outlines of coasts and islands, and the directions of chains of mountains, it is that of the geologist to assign the positions and courses of the strata by which these have been modified or determined. Geology teaches the Geographer the nature of the changes by which lakes have been obliterated, by which rivers have changed their courses; it conducts him from the mountain to the plain, and shows him why that which was once sea is now firm land. In contemplating the rocks of Niagara it foresees a period when that torrent shall no longer plunge into the abyss below; and, in viewing the fires of iEtna, it detects the causes that elected the splendid colonnades of Staffa and Sky. Of the Distribution of Sea and Land. The most prominent circumstance in the surface of the earth relates to the general distribution of sea and land; and if that which appears to be the next