228 



Fig. 3 



On a Mode of erecting light Vaults 



Fig. 5. 



unite in a point, as in a simple-pointed arch, at the ribs or 

 groins only, and not in the intermediate spaces. In the latter 

 portions they form rather a very acute ellipse; and the wall- 

 scutcheon * also has this form not unfrequently, indeed almost 

 universally, where there is not introduced in this part some 

 ornamented band or moulding. Hence the vertex of these 

 intermediate compartments is higher than the vertex of the 

 diagonal ribs, and forms a flat arch from their point to the wall, 

 as is manifest from the section in Fig. 6. 



* The portion of the wall, bounded by the arch, resembling an inverted escut- 

 cheon. 



