GROUND, ROCK, WATER 131 



from their effect, and in the light of his appreciation convey some 

 part of his inspiration to the beholder of his own small work. 



In whatever one of these ways he deals with natural landscape, knowl- 

 edge of the natural forms is a prerequisite to good design. This knowl- 

 edge can be obtained only by patient study of the forms themselves. 

 This chapter can do no more than consider a few examples from a 

 great number of forms, and discuss a few of the simpler considerations 

 out of vast possibilities of appreciation and inspiration. 



In ground forms large and small, the landscape architect finds the 

 three simple fundamental form unities, the convex, the concave, and 

 the plane. He studies hills and mountains, or valleys, or plains, and 

 again he makes in his own work similar forms and relations of forms, 

 of a size possible of production within his limited powers. 



From the multitude of shapes of hills and mountains, the designer Hills and 



might differentiate for purposes of discussion three classes according if *? l< ^* r; 



i i r 1. ' t 11 i 11. i i Typical Forms 



to the way in which the attention tails on their modeling and on their 



outline. There are hills which are crouching and comfortable, round- 

 topped, gentle-sloped, merging by imperceptible degrees into the sur- 

 rounding ground surface. (See Plate 22.) The attention which 

 follows their surfaces or their silhouettes against the distant sky may 

 run as readily away from their top as towards it, and is definitely ar- 

 rested nowhere along the line. Such hills are individual because they 

 lift themselves as considerable masses above the neighboring landscape, 

 but their surface is sequential with the surrounding forms. As their 

 height becomes less and their slopes less steep, they lose their indi- 

 viduality, and become at length merely undulations of a general sur- 

 face. Such hills may be the results of many different geologic causes, 

 but they are often produced by long-continued erosion or deposition of 

 soft materials. They may perhaps be left standing, first current-cut 

 and then rain-worn, above the flat-bottomed valleys of the lower reaches 

 of a river, being the remnants of a former plain, all the rest of which 

 has been carried away by the stream ; or they may be moraines or drum- 

 lins, masses of debris carried and at last deposited by the ice or by the 

 under-ice water of a glacier. 



There are mountains which are aspiring and individual, having a 

 definite summit in which the lines of the slopes culminate and on which 



