Geology. — On the Crust of the Earth. 291 



limited sense, comprehending only the mineral structure of rocks, 

 their relative position, and the fossils embedded in them. Al- 

 though the naturalists who have restricted their investigations 

 to these branches, have added to the general stock of informa- 

 tion, yet in such hands the study could not rise to the dignity of 

 a science. The origin of mountains and valleys, the changes of 

 the bed of the ocean, the action of rivers and nature of volcanoes, 

 and the highly liberal study of comparative anatomy, were all 

 excluded by this narrow field of observation, and with them all 

 the high philosophical views of the harm.ony of nature, by the 

 aid of which Geology may claim to be considered as a study 

 which leads to the knowledge of all natural science. Such is the 

 definition we vi'ould give to our favourite pursuit. 



In this Essay we propose to speak of that superficial part of 

 the globe which is called the crust, and which has been vari- 

 ously exposed to our observation either by the action of natural 

 agents, or by human labour. It is from the geological pheno- 

 mena thus disclosed, that we become acquainted with the rela- 

 tion in which Geology stands to all the physical sciences. Let 

 us first begin with the surface upon which we stand, and let us 

 suppose an individual whose mind has never been awakened to 

 this subject, contemplating, for the first time, the nature of that 

 surface, the sublime height of the mountains, the profound val- 

 leys, the extensive plains without hills or vales, the oceans, lakes 

 and rivers, and the thousand irregular beauties which give so 

 much grace to the face of nature. Yet would this superficial 

 aspect perhaps awaken no further idea with him, than that the 

 earth was a homogeneous mass of rocks and clays and sands, as- 

 sembled without order and design. But at the sea shore, where 

 the rocks have been worn down to mural escarpments, he will 

 perceive the beach to be covered with shingles or pebbles, tri- 

 turated against each other, and thus divested of the angular 

 form they had, when first broken off from the parent mass, 

 where they once were, as geologists say, in situ, or in place. 

 These will at once remind him of the rounded pebbles of a simi- 

 lar character found on the dry land, almost universally, and far 

 above the level of the sea; in many instances thousands of feet 

 above the marine level. The moment he begins to think of the 

 cause which could have produced this agreement betwixt 

 pebbles found in such dissimilar situations, he enters upon the 



