50 The Principles of Fruit-growing 



mer night can scarcely fail to notice the chillier air of the 

 depressions. This escape of the cold air is the secret of 

 much of the success of fruit-growing on rolling and sloping 

 land; and this fact explains the importance of giving 

 great attention to the selection of the site and aspect 

 when setting a plantation of the tenderer fruits. Barden 

 and Eustace (Mich. Bull. No. 63) give a picture (drawn 

 in Fig. 1), of a peach-orchard containing a pocket in the 



Fig. 2. The frosty belt on a hillside below a wood. 



region X in which buds are frequently destroyed by late 

 frosts, whereas those in the region escape uninjured. 



Features of such little apparent importance as not 

 to appeal to the fruit-grower often exert great influence 

 on the quiet movements of air. A frequent case is this: 

 A strawberry field ia on a gentle slope, and on the upper 

 side is a wood. In time of frost, the only injury occurs in 

 a belt two or three rods wide just against the wood, in the 

 very place where the greatest immunity was expected. 

 This is probably because the slight bodily movement of 

 the air down the hillside and over the forest strikes 

 obliquely downward from the edge of the wood-top, and 

 leaves a narrow belt of dead air against the timber (as at 

 A m Fig. 2). 



The atmospheric drainage is marked only in still air. 

 Winds mix up the air, and bring it all to a comparatively 

 uniform condition. The slightest obstacles may sufficiently 

 retard the movement to leave their impress in the distribu- 



