38 THE BROWN RAT IN THE UNITED STATES. 



traps that rats can not pass through will prevent such invasion of 

 dwellings. 



In cities, aside from dwellings, the sewers, wharfs, stables, and 

 outbuildings are the chief refuges for rats. Modern sewers are used 

 by the animals only as highways and not as permanent abodes; but 

 old-fashioned brick sewers often furnish nesting crannies. Openings 

 from sewers to streets may easily be screened against rats, but with 

 modern sewers this is unnecessary. 



Wharfs, stables, and outbuildings in cities should be constructed 

 with a view to exclude rats. Cement is the chief means to this end. 

 Old, tumble-down buildings and wharfs should not be tolerated in 

 any city, but should be condemned and destroyed. 



Almost everywhere, in country, village, and city, the wooden floors 

 of sidewalks, areas, and porches are commonly laid upon timbers 

 resting upon the ground. Under these floors rats are safe from most 

 of their enemies. Only municipal action can completely remedy 

 these conditions, but all such rat harbors should be destroyed and 

 replaced by cement floors. Considering durability, healthfulness, 

 and other advantages, this material is the cheapest that can be used. 

 The floors of wooden porches should always be well above the ground. 

 Rats often undermine brick walks or areas. 



Granaries, corncribs, and poultry houses may be made rat-proof 

 by a liberal use of concrete in the foundations and floors; or the 

 floors may be of wood resting upon concrete. Objection has been 

 urged against the use of concrete floors for horses, cattle, and poultry, 

 because the material is too good a conductor of heat and the health 

 of the animals suffers from contact with floors of this kind. In 

 poultry houses, dry soil or sand may be used as a covering for the 

 cement floor; and in stables, a wooden floor resting on the concrete 

 is just as satisfactory so far as the exclusion of rats is concerned. 



The common practice of setting corncribs on posts with inverted 

 pans at the top often fails to exclude rats, because the posts are not 

 high enough to place the lower cracks of the structure beyond reach 

 of the animals. The posts should project at least 3 feet above the 

 surface of the ground, for rats are excellent jumpers. But a crib 

 built in this manner, though cheap, is unsightly. 



For a rat-proof crib a well-drained site should be chosen. The 

 outer walls, laid in cement, should be sunk about 20 inches into the 

 ground. The space within the walls should be thoroughly grouted 

 with cement and broken stone and finished with "rich" concrete for 

 a floor. Upon this the structure may be built. Even the walls of 

 the crib may be concrete. Corn will not mold in contact with them, 

 provided there is good ventilation and the roof is water-tight. 



However, there are cheaper ways of excluding rats from either 

 new or old corncribs. Rats, mice, and sparrows may be effectually 



