28 ANIMAL COMPETITORS 



tar daubed about their holes, as also is caustic 

 potash. Where burrows are discovered in 

 banks or fields the inmates may be suffocated 

 by pushing into the holes wads of rags satu- 

 rated with bisulphide of carbon, as is practiced 

 against gophers ; but this is of little use in 

 buildings, for it escapes too easily. 



Rat-proof construction. All new or recon- 

 structed buildings should be made rat-proof. 

 This is best done by the use of cement. Even 

 then, when foundations and walls are made of 

 tight concrete, care must be taken lest drains 

 and other openings admit them. Outer doors, 

 especially those that give upon alleys, should 

 not be left open. Basement and cellar win- 

 dows of barns, stables, chicken-houses, etc., 

 should be screened with wire, so that they may 

 be left ajar for ventilation without danger. 

 Inner doors to vestibules are of great assist^ 

 ance. Even old cellars may be made rat-proof 

 by the use of cement at small expense. 



When wooden walls are built upon proper 

 foundations, the building may be made proof 

 against these and other noxious visitors by 



