132 VETERINARY HYGIENE 



surface. The constant traffic of a busy thoroughfare soon renders 

 this form of roadway very hard and durable. 



Mastic-Work is used for roadways, pavements, roofs, and lining 

 basements. The mineral rock asphalt is prepared by grinding and 

 mixing with a certain proportion of pure Trinidad bitumen and other 

 ingredients, after which it is moulded into blocks and stamped with 

 the manufacturer's name. These blocks are melted in metal pots 

 at the building, and " cooked " to the proper consistency, a certain 

 amount of pure bitumen and fine washed grits being added. This 

 work is spread in two layers, for horizontal work the joints being 

 lapped. The material is spread with the aid of a wooden float. 

 Being tough, it requires energy and kneading into position to ex- 

 clude all air or gas bells which, if left in, would result in blisters. 

 Mastic-work should never be executed in damp or wet weather. 



For excluding damp from basements it is applied to the face of 

 walls. This vertical work is slow and costly, but very effective if 

 properly executed and properly jointed to a damp course of the 

 same material extending under the whole area of the basement floor 

 (see section on Damp Buildings). 



FELTS AND BITUMINOUS ROOF COVERINGS. A variety of haired 

 felts and fibre felts are manufactured and supplied in rolls for 

 building purposes. 



For covering roof boarding, before the slating of the roofs is 

 applied, the cheapest form of felt is suitable. These felts consist 

 of a thin mat of vegetable fibre, impregnated with a solution of 

 bitumen or tar. 



A higher-grade material is manufactured, consisting of haired 

 felt similarly treated with a coal-tar oil or bituminous solution. 

 These haired felts are suitable for deafening floors by being nailed 

 to the top or bottom of the joists before the application of the 

 flooring or ceiling. They are also suitable for deafening purposes. 



Prepared roofings include such materials as (1) "Aqualite " 

 and " Plastique," composed of jute or canvas web, covered on both 

 surfaces with pure bitumen ; and (2) Vulcanised roofings consisting 

 of vegetable fibre with some form of vulcanised bitumen or other 

 substance which is calculated to exclude damp and resist fire. Such 

 roofings are known as " Ruberoid," " Rok," &c. These are suitable 

 for temporary or unimportant structures, where appearance is a 

 matter of little importance. They present these advantages, that 

 they may be rapidly and easily fixed by unskilled labour. 



TIMBER FOR BUILDING PURPOSES. The study of timber, its 

 growth, cutting, conversion, seasoning and characteristics, is a wide 

 subject demanding long application and experience. 



