162 OPEN AIE GRAPE CTJLTUEE. 



on a garden wall, on whicli I have been making 

 experiments at Slongli. It faces the south, and 

 against it, about the middle, a young grape vine is 

 trained. Two years ago I covered a portion of the 

 wall with thick black paint. The vine was divided 

 into two equal parts, one half was trained on the 

 painted, and the other on the plain wall. The sea- 

 son was so unfavorable last year, that scarcely any 

 out-door grapes came to perfection ; but those in the 

 blackened part of the wall were much finer than those 

 on the plain part. This year the success of my expe- 

 riment has been complete. The weight of fine 

 grapes gathered from the blackened part of the wall 

 was 20 lbs. 10 oz., while the plain part yielded only 

 7 lbs. 1 oz., being little more than one-third of the 

 other. The fruit on the blackened part of the wall 

 was also much finer, the bunches were larger and 

 ripened better than on the other half ; the wood of 

 the vine was likewise stronger and more covered with 

 leaves on the blackened part. 



'^ It is a generally known fact, that a black, unpo- 

 lished surfi\ce absorbs more rapidly than other colors 

 the sun's rays, and thereby becomes sooner heated. 

 It is equally well known that surfaces which absorb 

 heat more quickly, part with it more easily when the 

 source of lieat is withdrawn, and cool quicker. In 

 the summer time, when the days are long, the wall 



