INTERPRETATION OF LAND FORMS 147 



England outlined the problem and presented generalized 

 evidence. Hector (1863) in New Zealand pointed out 

 the significance of discordant drainage, the "hanging 

 valleys' 7 of Gilbert. The U-form, the broad lake-dotted 

 floor, and the presence of cirques and the process of 

 plucking were probably first described by LeConte 

 (1873) in America. The truncation of valley spurs by 

 glaciers pointed out by Studer in the Kerguelen Islands 

 (1878) was used by Chamberlin (1883) as evidence of 

 glacial scouring. 



Conclusion. 



During the past century many principles of land 

 sculpture have emerged from the fog of intellectual 

 speculation and unorganized observation and taken their 

 place among generally accepted truths. Many of them 

 are no longer subjects of controversy. Erosion has 

 found its place as a major geologic agent and has given 

 a new conception of natural scenery. Lofty mountains 

 are no longer "ancient as the sun," they are youthful 

 features in process of dissection; valleys and canyons 

 are the work of streams and glaciers ; fiords are erosion 

 forms; waterfalls and lakes are features in process of 

 elimination; many plains and plateaus owe their form 

 and position to long-continued denudation. Modern 

 landscapes are no longer viewed as original features or 

 the product of a single agent acting at a particular time, 

 but as ephemeral forms which owe their present appear- 

 ance to their age and the particular forces at work upon 

 them as well as to their original structure. 



It is interesting to note the halting steps leading to the 

 present viewpoint, to find that decades elapsed between 

 the formulation of a theory or the recording of signifi- 

 cant facts and their final acceptance or rejection, and to 

 realize that the organization of principles and observa- 

 tions into a science of physiography has been the work 

 of the present generation. Progress has been condi- 

 tioned by a number of factors besides the intellectual 

 ability of individual workers. 



The influence of locality is plainly seen. Convincing 

 evidence of river erosion was obtained in central France, 

 the Pacific Islands, and the Colorado Plateau regions 



