FROST PROTECTION. 373 



acres that the company extended it over seventeen acres. 

 *********** rpk e proposition embraced 

 in the covering is to prevent the warm air from leaving the 

 immediate vicinity of the trees at night. During the day 

 the earth and trees become warm, but as night cools the 

 atmosphere, the process of radiation sets in, and the heat 

 from the earth and the trees is carried off, the cold, frosty 

 atmosphere taking its place. The idea was conceived of 

 covering the orchard with canvas, which could be rolled 

 up in the morning and let out at night. One acre was 

 covered in this way, but it was found to be too expensive 

 and unstable, as the canvas would get wet and decay. The 

 present method costs about f 450 an acre. The fruit borne 

 by the trees under this covering has matured perfectly 

 and the covering serves two purposes, i. e., protecting 

 the trees from the effects of frost, and from excessive heat 

 in the summer. 



The posts are 3x4 redwood, 18 feet long. The trees 

 are so planted that the posts are placed 21 feet 3 inches 

 apart each way, setting them 3 feet in the ground, thus 

 allowing about 15 feet in the clear for height of the trees, 

 which is sufficient for most Navel trees. These posts are 

 connected by pieces of 1x4 pine suitably braced, on top 

 of which another strip of 1x4 has been securely nailed to 

 prevent the whole from swaying sideways with the weight 

 of the cover. This, when placed in position, is braced 

 horizontally with braces of 1x3 pine, 7 feet long. Thus 

 is secured a framework that is quite rigid and on which 

 a man may walk freely, provided he has a head clear enough 

 to walk on a four-inch strip. 



Over this were stretched galvanized-iron wires, diag- 

 onally, of No. 11 wire, which are securely stapled on top 

 of each post and to the horizontal braces. These diag- 



