ARCHITECTURE. 153 
intercolumniation (J. 38, fig. 19). Immediately afterwards appeared the 
second form, which is very high and pointed, the centres of the component 
arcs lying far beyond the sides of the arch (pl. 36, fig.3). The next form is 
that of the most beautiful and regular pointed arches. It is called the 
equilateral arch, the centres of the arcs being in the springings of the arch 
(jig. 4). The fourth form is the lancehead arch, which is constructed from 
the same centres, but the arcs are extended below through the level 
of the centres (jig. 5). The fifth form is the overtopped arch, whose 
curves are also described from the same centres as in the two last, whilst 
the extensions below their levels are in straight lines (jig. 6). This arch is 
employed in the same cases as the overtopped semicircular arch. The two 
forms belonging to the 15th century are: 1. The prolonged pointed arch 
(jig. 7°). The curves forming the sides of this arch are composed of two 
arcs, the lower one described from the opposite springing as centre; the 
upper one from a centre a little distant from the centre of the intercolumni- 
ation. 2. The counter arch, whose arcs are below the level of their centres, 
each of which is on the same side of the arch as the are to which it belongs 
(fig. 8). This arch occurs frequently in English architecture. The trefoil 
arch occurs also in the pointed style in the 11th and 12th centuries; after- 
wards much corrupted ; and in the 15th century in England and France in 
the flowing or flamboyant style. 
The ass’s-back arch, which is called Tudor arch when it is very flat, has 
sides composed of two arcs, but differs from the prolonged pointed arch in 
this, that the centre of the upper arc is above the arch as in the counter 
arch, whilst that of the lower is below the arch, and the entire side conse- 
quently a wave line (jig. 9). 
The basket arch (fig. 76), which is a frequent form of our day, appears 
very flat in the middle ages, especially in France and England; more 
rarely in Germany, and then only in private dwellings. An example of 
this latter form is given in jfig.10. It is not to be confounded with the 
horizontal top with rounded corners (jig. 11), which is no arch proper, the 
corners only describing arcs of a very short radius. In the time of the 
renaissance (revival of architecture) pointed arches gradually disappear, 
superseded by flat, elliptical, and semicircular arches. 
The decoration of the archivolts consists either in the introduction of stone 
of different colors (fig. 12), which was the prevalent manner of the Moorish 
and Byzantine styles; or they are moulded (jig. 18); or the stone wedges 
project more or less (jig. 14). An English mode of constructing the archi- 
volt is curious, having a zigzag or toothed ornament (fig. 15). There are 
also lobed archivolts (jig. 16) or counter lobed (jig. 17). The latter were 
developed in the 15th century so as to exhibit the trefoil arch on a small 
seale (fig. 18) by prolonging and notching the points between the counter 
lobes. 
The archivolt of the pointed arch was at first entirely simple, and at 
most received an astragal for decoration. Afterwards it was covered with 
mouldings, with a view of disguising their true dimensions, and giving 
them a lighter appearance. The first decorative construction was the com- 
153 
