The Natural Style in Landscape Gardening 



ventory of principles, every one of which exercises 

 a quite decided influence upon the forms of native 

 landscape. It will answer the present purpose, 

 however, to point out that these are the simple prin- 

 ciples of physics as expressed in geology and physi- 

 cal geography. In order, therefore, to understand 

 the unit forms of natural landscape we must know 

 something of geology and of physical geography. 

 One then grasps the landscape result along with 

 the geologic cause. It is plain that the Berkshire 

 Hills must have rounded tops because they were 

 ground down by the glaciers, while the Rocky 

 Mountains will have acute tops because they are 

 recently broken up by volcanic action and have 

 never been eroded at the peaks. It is plain that the 

 sand dunes of Lake Michigan and New Jersey 

 must lie in billows; that great areas of the lower 

 Mississippi Valley must be in swamps; and that 

 the west slope of the Cascade range will support 

 a very different flora from the dry east slope. 



These great geologic forces are then the deter- 

 mining factors in the formation of aU the great 

 natural types of landscape as enumerated in Chap- 



46 



