28 THE BROWN EAT IN THE UNITED STATES. 



similar instance in that city where pipes were gnawed by rats, but 

 fortunately it occurred when the inmates were awake. 



The most common way in which rats cause fires is by gnawing away 

 the insulating covering from wires used in electric lighting, where the 

 wires pass under floors or inside of partitions. The insulating mate- 

 rials are used for nests, which rats often build of combustibles placed 

 in contact with the naked wires. Insurance companies, a few years 

 ago, estimated the fire loss in the United States due to defective 

 insulation of wires at $15,000,000 yearly; and since rats and mice 

 are the chief agents in impairing the insulation after the wires are in 

 place, a large part of the above sum must be charged to these animals. 



Rats often do mischief by gnawing the insulating covering of tele- 

 phone wires to obtain the paraffin which it contains. The accom- 

 panying illustration (fig, 1) is from a photograph of wires gnawed by 



Fig. 1.— Telephone wires gnawed by rats. 



rats August 20, 1908, where these wires passed through a partition 

 in rooms occupied by the Biological Survey. 



DAMAGE TO BUILDINGS AND FURNITUEE. 



The damage to houses and furniture by rats constitutes a large item. 

 They burrow under foundations or through the plaster in a stone wall 

 and admit streams of water that eventually weaken or undermine the 

 structure itself. They seem to be able to penetrate almost every- 

 thing except stone, brick, cement, glass, and iron. They gnaw into 

 a grain bin, or through a wainscoting, a floor, or a door in a single 

 night. In the same way they enter chests, wardrobes, bookcases, 

 closets, barrels, and boxes for the stores within. Almost every old 

 dwelling in the country bears abundant evidence of its former or pres- 

 ent occupancy by rats. Often depreciation in value of houses and 

 furniture is due largely to marks left upon them by rats — marks 

 that paint and varnish can not hide. 



