FUMIGATION. 161 



"In order to render tlie canvas used for fumigation per- 

 fectly air-tiglit, to prevent the gas escaping, tlie tents 

 have been treated with a light coat of linseed oil. The 

 great objection to the oil has been that it had a tendency 

 to stift'en the canvas and add considerably to its weio^ht, 



■J O ' 



so a cheaper and more flexible prepai'ation was sought. 

 The following mixture, used by Commissioner Scott, of 

 Los Angeles country, California, during the past season, 

 made the tents gas-tight, and left the canvas soft and 

 j^liable. The chief essential ingredient is a supply of 

 common 'Prickly Pear Cactus' (^Opuntia Emrelmanni), 

 that grows in abundance in the southern countries of the 

 state. It is a flat-leaf species, and parties living in sec- 

 tions to which it is not indigenous could have it sent in 

 boxes. To make the cactus extract, chop up enough 

 cactus to fill a barrel two-thirds full ; then fill up with a 

 barrel of cold water. It should stand for 24 hours, when 

 it will be ready for use. Do not prepare more than is 

 required for immediate use, otherwise it will become sour 

 and worthless. Stir well, then strain ten gallons of the 

 liquid into another tub or barrel ; dissolve 2 lbs. of 

 common glue, and add to the cactus extract, with suflR- 

 cient yellow ochre or Venetian red to give it a good body. 

 After thoroughly mixing the ingredients it is ready for 

 use. Both sides of the canvas should be painted, and the 

 dressing well rubbed into the fibre with a flat paint brush." 

 [It is possible that our common ' Prickly Pear ' ( Opuntid) 

 might answer the same purpose. At any rate, it would 

 be worth a trial, as plenty of material could be easily 

 obtained here. — C.F.] 



" If oil is used, the canvas should be spread out and 

 thoroughly dried before it is rolled up, or it is liable to 

 be destroyed by spontaneous combustion. When dry 

 there is no danger in this." 



The above has been taken from the Bulletin of the 

 Califoruian State Board of Horticulture, the information 

 having been prepared by Mr. Craw, whose opportunities 

 for experimenting and general knowledge of the whole 



11597. L 



