AA 
ConsTRUCTING ARCHES, AT7 
AT the spring of the arch, stones of a considerable length 
“were used, having the inner ends ctit, so as to suit the curva- 
ture of the arch. Six such layers were laid on each side, in 
the manner stoiies are placed, in what is generally termed the 
Egyptian arch. ‘The upper layer having a groove, five inches 
wide, and two in depth. 
BBBBB On arriving at this height, stones of a smaller size were 
CcCceeé 
made. use of, each having a groove cut in two adjoining faces, 
two inches in depth by four in breadth, with corresponding 
projections on the opposite sides. 
‘THEsE stones oe so placed, that when a layer was com- 
pleted, there appeared a channel or groove the whole length 
of the building ready to receive and bind to it by their projec- 
tions, the next row, of stones when applied. The: stones 
were of a fine sort of free stone easily cut. Common cement 
was. used. 
Eicnr layers of the stones last described, having been 
placed on both sides, each layer occupying about six inches 
of the curvature of the arch, it becomes necessary to prevent 
the work, if carried on, from falling inwards. A space of ten 
feet in length, on each side of the unfinished arch was marked 
Fig. 16 2 off, and at these points two strong horizontal beams, were 
VOL. XIV. 
6 F 
