Geographic Methods in Geologic Investigation. 13 



gratuitous assumption of great results from vague causes. Causes 

 must be shown to be not only appropriate in quality, but suf- 

 ficient in quantity before they can be safely accepted. But the 

 geographic argument as expounded by the English school deals 

 almost entirely with processes and neglects a large class of results 

 that follow from these processes. Much attention is given to the 

 methods of transferring the waste of the land to the sea and 

 depositing it there in stratified masses, from which the history of 

 ancient lands is determined. But the forms assumed by the 

 wasting land have not been sufficiently examined. It was recog- 

 nized in a general way that land forms were the product of denu- 

 dation, but the enormous volume of material that had been 

 washed off of the lands was hardly appreciated, and the great 

 significance of the forms developed during the destruction of the 

 land was not perceived. 



Button says a little about the relation of topography to struc- 

 ture; Lyell says less. The systematic study of topography is 

 largely American. There is opportunity for it in this country 

 that is not easily found in Europe. The advance in this study 

 has been made in two distinct steps : first, in the East about 

 1840 ; second, in the West about 1870. The first step was taken 

 in that historic decade when our early State surveys accomplished 

 their great work. The Pennsylvania surveyors then developed 

 topography into a science, as Lesley tells us so eloquently in his 

 rare little book " Coal and its Topography," 1856, which deserves 

 to be brought more to the attention of the younger geographers 

 and geologists of to-day. It presents in brief and picturesque 

 form the topographical results of the first geological survey of 

 Pennsylvania. It shows how Lesley and the other members of 

 that survey " became not mineralogists, not miners, not learned 

 in fossils, not geologists in the full sense of the word, but topog- 

 raphers, and topography became a science and was returned to 

 Europe and presented to geology as an American invention. 

 The passion with which we studied it is inconceivable, the details 

 into which it leads us were infinite. Every township was a new 

 monograph." (p. 125.) Some of the finest groups of canoes and 

 zigzags developed on the folded beds of the Pennsylvania Appa- 

 lachians are illustrated from studies made by Henderson, Whelp- 

 ley and McKinley, and they certainly deserve the most attentive 

 examination. I often feel that they have been of the greatest 

 assistance in my own field work, especially in the efforts I have 



