THE WAR ON INSECTS 283 



is made in barrels into which live steam is led from a 

 central boiler. These plants vary so greatly that only 

 the principles upon which they are built can be stated. 

 In all cases there is a drop from an elevated steam pipe, 

 reaching to the bottom of the barrel, where there are 

 usually cross arms of perforated iron pipe to permit 

 the steam to get to all parts of the mass and prevent 

 irregular cooking. The proper amounts of lime, sulphur 

 and water are put into the barrel, and the steam is 

 turned on for an hour or longer, until the combination 

 is completed. 



It is also possible to make a good combination of 

 lime and sulphur by the heat of slacking lime alone, or 

 by using potash in addition to the lime to produce the 

 proper degree of heat. It requires heat to combine the 

 lime and sulphur and it matters little whence this heat 

 comes; whether from burning wood or coal, from steam, 

 or from slacking lime, soda or potash. The wash is 

 effective in proportion to the completeness of the 

 combination and the thoroughness of the application. 



To make the lime, soda and sulphur combination 

 put into a barrel 22 pounds of best quality stone lime 

 and add hot water enough to start slacking. While 

 this is in progress sift in 10 pounds of flowers of sul- 

 phur, stirring and adding hot water as needed until 

 the mass is well reduced. Then add n pounds more of 

 lime with more hot water, and sift in 7 pounds more of 

 sulphur while this is slacking. Before it is done steam- 

 ing, stir in ij pounds of caustic soda which will cause a 

 violent boiling, and when this begins to subside add an 

 equal amount and then again another ij pounds, 

 making 4^ pounds altogether. Keep stirring and 

 adding hot water slowly until the combination is com- 

 pleted. Then add hot water to make 50 gallons and 

 apply at once. 



