The London Building Act of 1894 and its amendments set forth with regard to roofs erected in the London district that every structure on a roof is to be covered with slate, tile, metal or other incombustible material, except wooden cor nices and barge boards to dormers not exceeding 12 in. in depth, and doors and windows and their frames. Every dwelling-house or factory above 3o ft. in height and having a parapet must have means of access to the roof. The pitch of the roofs of warehouse buildings must not exceed 47°, and those of other buildings 75°, but towers, turrets and spires are excepted. In domestic buildings not more than two storeys are to be formed in the roof, and if the floor is more than 6o ft. above the street level fireproof ma terials must be used throughout and a sufficient means of escape provided.
The Building and Health Laws and Regulations and Amend ments affecting the city of New York are similar to those of Lon don. They give very full working details as to the strengths of materials required to be used and the wind pressure to be pro vided against. They provide that where a building exceeds three storeys or 4o ft. in height and the roof has a pitch of over 6o°, it shall be constructed of iron rafters and be lathed with iron or steel inside and plastered or filled in with fireproof material not less than 3 in. thick and covered with metal, slate or tile.
principal reference books on this subject are the following:—G. L. Sutcliffe, The Modern Carpenter, Joiner and Cabinet Maker; J. Gwilt, Encyclopaedia of Architecture.; F. E. Kidder, Trussed
Roofs and Roof Trusses; J. Brandon, Analysis of Gothic Architecture; A. Pugin, Ornamental Gables; M. Emy, L'Art de la charpenterie; Viollet le Duc, Dictionnaire; J. K. Coiling, Details of Gothic Archi tecture; G. Ellis, Modern Practical Carpentry; Jaggard & Drury, Architectural Building Construction; Blake, Roofs & Roof Coverings; J. W. Riley, Carpentry & Joinery; C. F. Mitchell, Building Construc tion; Rivington, Building Construction.
(Corvus frugilegus), throughout a great part of Europe, the commonest of the crow tribe. Besides its gregarious habits, which are distinctive, the rook is distinguished from the rest of the Corvidae by losing at an early age the feathers from its face, leaving a bare, scabrous and greyish-white skin visible at some distance. In the rare cases in which these feathers persist, the rook may be known from the crow (q.v.) by the rich purple gloss of its black plumage, especially on the head and neck, as well as by its voice. The sexes are very similar. It nests in colonies on large trees (occasionally on buildings), making a strong nest of twigs and earth and using it year after year. The three to five green eggs, marked with grey and brown, are laid in early April. In Britain the rook is resident and stationary, but in most of Europe it is either a summer or winter visitor. Its food is very varied, but includes a high percentage of noxious insects. The bird is thus of great value to the farmer.