62 OF PAINTING. BOOK I. 



The principles of grouping are the chief guides in thinning 

 old plantations or clumps, and even in pruning single trees : 

 indeed there is no one principle of painting more extensively 

 applicable in rural improvements. 



4. The knowledge of perspective and optics is of very great 

 use both in architecture and the. laying out of grounds. In al- 

 tering or improving old places, or in uniting scenery where 

 trees already exist, it is one of the leading principles. In hilly 

 or mountainous countries, when young plantations are to be 

 made on their sides, it is of great importance. By attending to 

 it in forming their outlines, the hill may be made to assume a 

 woody or clothed appearance, by covering only a very few 

 acres, and thus preserving most of the ground which by the 

 plantations will often be rendered of double value, either for 

 pasturage or aration. In the north of Scotland I have had 

 frequent opportunities of contrasting this practice with that of 

 making only one large inclosure unconnected with every thing 

 else ; which, while it had no more the appearance of massive- 

 ness than the other, covered the whole surface, and left none 

 for agricultural purposes. 



5. The next advantage to be derived from the art of painting 

 is of less importance than the former ; but still has its use, 



