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VETEEINAEY HYGIENE 



economy to put a damp proof course in the wall, and then 

 saturate the foundation either by having no gutter or a 

 defective one. 



The style of roof employed is either the ordinary closed 

 one or the open roof. The latter may be described as a 

 contrivance for the admission of fresh or the escape of 

 impure air through the roof. It is usual to provide this 

 opening along the ridge (Fig. 84), either for its full length 

 or at intervals protected by a louvre which keeps out the 

 rain. But the roof need not necessarily be open at the 

 ridge, it may open midway between the ridge and eaves as 

 in Fig. 85, a plan largely adopted in arranging the ventila- 

 tion of covered yards for cattle. 



If slates are used a good ventilating roof may be obtained 

 by not allowing the edges to meet, the method being known 



Fis. 84. — Ridge Ventilator with Louvr* 



Fig. 85.— Open Roof. 



as open slating. In the space left between the edges — 

 which is about 2^ inches — the -air finds its way through an 

 opening which is only the thickness of a slate, but which 

 when spread over the whole roof represents something very 

 considerable. 



Wood covered with felt or waterproof paper makes a 

 useful light roof for small buildings, but is hardly suf- 

 ficiently substantial for permanent ones. 



Though there is a prejudice against them in some 

 quarters, galvanized iron both for walls and roof will prob- 

 ably play an important part in the future. Buildings in 

 galvanized iron are now made in convenient sizes for many 

 agricultural purposes ; for stables, cow houses, or boxes for 



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