CHAPTER X 

 THE PRINCIPLES OF LAND SCULPTURE 



A PHYSIOGRAPHIC CLASSIC 



It is safe to say that the chapter on "Land sculpture," occupying the last 50 pages of the 

 Henry Mountains report, has been more generally read and apprehended than the preceding 

 chapter of similar length on the conditions of laccolithic intrusion. The discussion of the 

 laccolithic problem possessed, in view of the frequent use that it made of algebraic equations, 

 a mathematical turn which was unattractive to many readers, and it moreover had, in view of 

 the rarity of well-defined laccoliths, little relation to the experience of most geologists. On 

 the other hand, the discussion of land sculpture, although penetratingly analytical, was sim- 

 pler in its manner of presentation and was also of universal application. More important still, 

 it was a timely chapter, for, although published less than a half century ago, it appeared at 

 an epoch when only a good beginning had been made toward recognizing the operation of slow- 

 acting erosional processes, not simply in furnishing detritus for marine deposition, as Lyell 

 and other uniformitarian strati graph ers had taught, but also in the shaping of the surface of 

 the land from which the detritus was taken, as American observers were teaching. Gilbert 

 was still several years later of the opinion that the rational treatment of land forms should be 

 brought to the attention of geological readers and observers, for he wrote in a preliminary report 

 on Lake Bonneville: "We are unaccustomed to think of the ordinary forms of land as a work 

 of sculpture, but that is none the less their origin." J The sculpturing work of erosion there- 

 fore needed at that time precisely the kind of deliberative elaboration that it received in the 

 Henry Mountains report. 



Powell's Exploration of the Colorado Eiver of the West and his Geology of the Eastern 

 Part of the Uinta Mountains, both of which were issued shortly before the Henry Mountains 

 report, had contributed valiantly toward opening the way for Gilbert's elaborate discussion of 

 land sculpture, for they emphasize the conviction previously announced by Newberry that 

 even the greatest of chasms was wholly the work of ordinary erosional processes. They also 

 explained that the downward erosion of an " antecedent " river may be faster than the upward 

 heave of a mountain range athwart its path, and they introduced, along with the excellent 

 term "base level," the general principle that the long-continued action of weather and streams 

 must eventually reduce any still-standing land mass, however extensive, elevated, and resistant 

 it may be, to a lowland sloping very gently to the shore of its adjoining sea. Powell summar- 

 ized this geological philosophy in two striking sentences: "Mountains cannot long remain 

 mountains; they are ephemeral topographic forms. Geologically all existing mountains are 

 recent; the ancient mountains are gone." (Uinta Mountains, 196.) He also gave some con- 

 sideration to the processes by which the waves of the earth's surface, raised at a time of crustal 

 storm, are slowly flattened down during a long period of crustal calm, but his analysis of this 

 problem was in several respects less detailed than Gilbert's. However, Powell's explanatory 

 discussions directed attention to the problems of degradation and sculpture and placed the 

 scientific public in the attitude of asking for "more." Gilbert's, chapter on "Land sculpture" 

 therefore found ready attention from a large circle of readers who were eagerly waiting for 

 further instruction on the subject that it treated. 



It is nearly always the case that an essay such as this one of Gilbert's, clear as may be the 

 treatment of its problems, gives no indication of the circumstances which prompted its com- 

 position. They are revealed, however, in a letter that Gilbert wrote to a distant correspondent 

 nearly 30 years later, in September, 1905. He then explained: 



My youth was passed and my early geologic studies were made [he would have called them "geological" 

 at the time of their making] in a glaciated region. When I afterward studied the mountains of the Great Basin 



>U. S. Qeol. Survey, 2d Ann. Ept., 1881, 83. 



