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 conerete, 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 
