32 STABLE BUILDING AND STABLE FITTING. 



lighting and ventilation, with a shutter on butt hinges in each, 

 and a smaller gable with louvres at the opposite end. This 

 roof is covered with corrugated tiles. 

 North London The roof illustrated by Plates 40 and 41 is covered with 

 Tramways Vielle Montagne zinc of the Italian pattern, and therefore, but 

 for the above-named provision, might have been made lighter 

 in some of its members. This is laid upon i-inch diagonal 

 boarding, wrought on the underside for painting, with wood 

 rolls or rafters if inch wide nailed to it, the latter being 

 rounded to receive the corrugations c^ the zinc, as shown on 

 Fig. 12. Where the boarding is dispensed with, the rafters are 



3 inches by ij inch. 



Fig. 12. 



Zinc rcofs. 



Templates. 



Wrought 

 iron roofs. 



The additional depth is also used with the boarding, and 

 allows a space for air between the two materials, an advantage 

 (where zinc of sufficient thickness is used) in a stable or corn 

 store. 



The pole plates, purlins, and longitudinal timbers of the- 

 stables above referred to rest on small York stone templates 

 9 inches by 9 inches by 3 inches, built into the walls, whilst 

 those of the girders, to which the heel posts are tenoned, are 

 18 inches by 9 inches by 3 inches. It is not a good plan to secure 

 the heel posts to any members of the roof, the timbers of which 

 should be made of sufficient section to transmit its weight to 

 the external walls. In this case the longitudinal girders do not 

 support the principal of the roof, and a slight camber is given 

 to the tie-beam. 



For the covering of yards and sheds, where the span is over 

 30 feet, wrought-iron trusses are preferable to wood ; although 

 the purlins to receive the boarding should be of the latter 

 material. These may be secured to the principal rafters either 



