BEICK AECHES 



43 



window sill in the case of a window opening. These planks should be 

 carefully placed and. if necessary, wedged up, in order to support the 

 centering as solidly as possible. 



In the case of the door opening (Fig. 35) the centering would be 

 placed in position behind the door-frame. The core would then be built 

 on top of the door-frame, the centering being used as a guide in building 

 it. Next, the arch ring would be built on top of the continuous surface 

 formed by the core and the centering. 



While building in window frames (see Fig. 37) for stables, byres, etc., 

 two half-centerings would require to be used, one being fixed in front 



Fig. 37. 



of the window frame and one behind. In the case, however, of dwelling 

 houses (and sometimes in that of stables, byres, etc.), the inside centering 

 is unnecessary, its place being taken by a permanent" 4£" by 3" lintel 

 — set with the greater dimension horizontal — upon which the core and 

 arch are built. Note from Fig. 37 how the bricks forming the lower 

 arch ring are cut away slightly as they approach the jambs, so as to 

 allow the window frame to penetrate the arch ring to an extent of 

 about V 2 inches at each springing. The bricks forming the jambs are 

 also cut away, as at A and B, to allow the window frame to penetrate 

 each jamb to a depth of about 1 inch. 



