144 LANDSCAPE DESIGN 



can be completely screened from the rest of the landscape, and is ex- 

 tensive enough so that when it is so screened it will not appear absurdly 

 small in relation to the necessary paths or steps or human figures which 

 will be found in it, then it may be possible to arrange the rocks on the 

 assumption, as it were, that they have been put there by some defi.nite 

 working of natural forces, and so to produce a naturalistic composition 

 good in itself and not betrayed by its surroundings. If the rocks are 

 used in connection with existing natural rock, then the character of 

 that natural rock of course must be carefully studied and followed in 

 the new work. 



In his use of rocks in design, the landscape architect must not lose 

 sight of a few elementary geologic facts. The original substance of 

 the earth's crust was rock, and much of its modeling still is plainly 

 based on rock form, but in the course of ages of breaking down and trans- 

 portation of fragments, mostly by water, the rock has commonly come to 

 be overlain by earth which has assumed its own forms under the forces 

 which created and transported it. On the surface of the earth to-day, 

 we find rock, as a striking element in landscape, still existing in primi- 

 tive ledges, or broken away by frost and still lying in large masses show- 

 ing by their stratification and cleavage the structure of their original 

 ledge, or carried away from their first site by ice or water and worn by 

 the friction of its transportation into more or less rounded forms, or 

 broken and worn into still smaller fragments, the pieces losing their 

 individuality as the}'' become parts of a deposit of small bowlders or 

 gravel or sand. There is bound to be, therefore, a natural relation 

 between the kind and character of the rock and the larger forms in 

 which it is found. It is idle to attempt to imitate a naturalistic ledge- 

 outcrop with a collection of water-worn or ice-worn bowlders, for both 

 their rounded form and their varied material would preclude any 

 natural effect. Equally impossible is it to imitate a stream-cut 

 earth-and-bowlder bank by placing angular stones at random on the 

 surface of a gravel slope. 

 Bowlders Bowlders are usually found exposed, in nature, where the softer 



material with which they were once associated has been removed by 

 some natural force of erosion. Bowlders are found, for instance, 

 grouped in New England fields where the softer material of the glacial 



