Insect Exteuminators. 109 



the most simple way, and one making the least trouble. 

 For a house 100x3 8, four troughs are recommended. 



Fig. 27. 



In order not to have any liquid remain unevaporated, 

 they may be constructed as shown in fig. 27. A size 

 three feet long by four inches deep and wide, will be 

 sufficient. To prevent them from leaking where the 

 pipe passes through the ends, make a running thread 

 on each piece thus running through, say six inches 

 long, and this will admit of using a rubber packing, 

 and a nut on each side of the galvanized iron, render- 

 ing it perfectly tight, and capable of resi&ting any ex- 

 pansion or contraction there may be in the pipe. If 

 the extract of tobacco is evaporated in these twice a 

 week, scarcely a fly will be seen, provided they are not 

 allowed to multiply and become mature before it is 

 applied. Another plan that is being used in some 



