A. It may be described as formed by the two upper sides of a triangle,
more or less obtuse or acute. It is generally considered as one of the
characteristics of the Anglo-Saxon style, where it is often to be met with
of plain and rude construction. But instances of this form of arch, though
they are not frequent, are to be met with in the Norman and subsequent
styles. Arches, however, of this description, of late date, may be
generally known by some moulding or other feature peculiar to the style in
which it is used.

[Illustration]

Q. What different kinds of round-headed arches are there?

A. The semicircular arch (fig. 1), the stilted arch (fig. 2), the
segmental arch (fig. 3), and the horse-shoe arch (fig. 4).

[Illustration]

Q. How are they formed or described?

A. The semicircular arch is described from a centre in the same line with
its spring; the stilted arch in the same manner, but the sides are carried
downwards in a straight line below the spring of the curve till they rest
upon the imposts; the segmental arch is described from a centre lower than
its spring; and the horse-shoe arch from a centre placed above its spring.

Q. During what period of time do we find these arches generally in use?

A. The semicircular arch, which is the most common, we find to have
prevailed from the time of the Romans to the close of the twelfth
century, when it became generally discarded; and we seldom meet with it
again, in its simple state, till about the middle of the sixteenth
century. It is in some degree considered as a characteristic of the
Anglo-Saxon and Norman styles. The stilted arch is chiefly found in
conjunction with the semicircular arch in the construction of Norman
vaulting over a space in plan that of a parallelogram. The segmental arch
we meet with in almost all the styles, used as an arch of construction,
and for doorway and window arches; whilst the form of the horse-shoe arch
seems, in many instances, to have been occasioned by the settlement and
inclination of the piers from which it springs.

Q. Into how many classes may the pointed arch be divided?

A. Into two, namely, the simple pointed arch described from two centres,
and the complex pointed arch described from four centres.

Q. What are the different kinds of simple pointed arches?

A. The LANCET, or acute-pointed arch; the EQUILATERAL pointed arch; and
the OBTUSE-ANGLED pointed arch.

Q. How is the lancet arch formed and described?