Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 685
That from this point upward their curvature should be so adjusted as tomake them all meet their fellows on the same horizontal plane, so that all theridges of the vaults may be on one level. The geometrical difficulty of such works led to what is called fan-traceryvaulting. If similar arches spring… … Fig. 1629. i ARCHITECTURAL CONSTRUCTION. 669
Mechanical drawing
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