536 CITRUS FRUITS AND THEIR CULTURE. 



tached, the tent is reinforced, but this is a matter in which 

 there is much diversity. The details of the construction 

 will depend somewhat on the size and kind of tent, and 

 will be referred to again, below. 



After the tent is made, it is treated in some manner 

 to make it gas-tight, so as to confine the gas better. Three 

 methods are used for this purpose, all of which seem to 

 give good satisfaction. 



The first method is to thoroughly treat the tent with 

 boiled linseed oil. It is applied freely with a brush, and 

 the whole cloth becomes saturated with it. The tent must 

 be kept spread out till quite dry, for the oil has a great 

 tendency to heat if not exposed freely to the air, and the 

 cloth chars and becomes rotten. If properly done, the 

 tent remains strong and tight, and is not too stiff. 



The second method consists in the use of sizing and 

 paint. The sizing is applied in the same manner as the oil, 

 and penetrates the fiber of the cloth in the same way. As 

 soon as this coat is dry it is followed by another of rather 

 thin flexible paint, sometimes on both sides; the result 

 being a perfectly tight tent with a very smooth surface 

 and fully as flexible as the oiled tent. The sizing protects 

 the fiber of the cloth, so there is no danger of heating. 



The third method is the saturation of the cloth by a 

 decoction of the chopped-up leaves of the common prickly- 

 pear cactus (Opuntia engelmani). This decoction is made 

 by filling a barrel two-thirds full of the chopped stems, 

 adding cold water till the barrel is nearly full; then let- 

 ting it soak tw^enty-four hours, when it is drawn off and 

 strained, and is ready for use. This decoction is seldom 

 used by itself, but other substances are added according 

 to the whim of the person treating the tents. Very gener- 

 ally a pigment like yellow ochre or Venetian red, is added 



