34 FUMIGATION METHODS 



cloth, filling the fiber in the same way, making it 

 when dried thoroughly gas-proof. As soon as the 

 paint is dry the sheet is covered with another coat of 

 rather flexible paint. When dry this coating makes a 

 perfectly tight tent, with a smooth surface and quite 

 as flexible and easily handled as the oiled tent. 



Still another method is used in some places. A 

 decoclion is made by filling a barrel two-thirds full of 

 chopped stems and leaves of the common prickly pear 

 cactus {Opuntia engelmani). Afterward the barrel is 

 filled with cold water and is allowed to stand twenty- 

 four hours. The liquid is then drawn off and ready for 

 use by adding a pigment, like yellow ochre or Venitian 

 red. Sometimes a small quantity of glue is added. 

 To prevent molding when not in use and folded, a small 

 quantity of tannin solution is added to the mixture. 

 This solution can be applied to the tents with a brush, 

 but where a sufficient quantity is on hand it is better 

 to soak the sheets over night in a vessel containing the 

 mixture. They should then be taken out of the 

 material, thoroughly drained, and spread out to dry. 

 This method, however, is not generally used, but has 

 given very satisfactory results, as the cloth is not 

 stiffened, and is made quite flexible and easily handled. 



