49 



" The paved bottom road-covering on Telford's plan is 

 formed by excavating the surface of the ground to a suitable 

 depth, and preparing the form for the pavement with the pre- 

 cautions as for a common pavement. Blocks of stone of an 

 irregular pyramidal shape are selected for the pavement, which, 

 for a roadway thirty feet in width, should be seven inches 

 thick for the centre of the road, and three inches thick at the 

 sides. The base of each should not measure more than five 

 inches, and the top not less than four inches. 



" The blocks are set by the hand, with great care, as closely 

 in contact at their bases as practicable ; and blocks of a suitable 

 size are selected to give the surface of the pavement a slightly 

 convex shape from the centre outwards. The spaces between 

 the blocks are filled with clippings of stone, compactly set with 

 a small hammer. 



" A layer of broken stone, four inches thick, is laid over 

 this pavement, for a width of nine feet, on each side of the 

 centre , no fragment of this layer should measure over two and 

 a-half inches in any direction. A layer of broken stone of 

 smaller dimensions, or of clean, coarse gravel, is spread over 

 the wings to the same depth as the centre layer. 



" The road-covering thus prepared is thrown open to 

 vehicles until the upper layer has become perfectly compact, 

 care having been taken to fill in the ruts with fresh stone, in 

 order to obtain a uniform surface. A second layer, about two 

 inches in depth, is then laid over the centre of the road- way ; 

 and the wings receive also a layer of new material laid on to a 

 sufficient thickness to make the outside of the road-way nine 

 inches lower than the centre, by giving a slight convexity to 

 the surface from the centre outwards. A coating of clean 

 coarse gravel, one inch and a half thick, termed a binding, is 

 spread over the surface, and the road-covering is then ready to 

 be thrown open to traveling. 



" In forming a road-covering of broken stone alone, the bed 

 for the covering is arranged in the same manner as for the 

 paved bottoming ; a layer of the stone, four inches in thickness, 

 is carefully spread over the bed, and the road is thrown open to 

 vehicles, care beiug taken to fill the ruts and preserve the sur- 

 face in a uniform state until the layer has become compact ; 

 successive layers are laid on and treated in the same manner 



