This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol5", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
In modern Classic work the windows have either square heads surrounded with an architrave mould (Fig. 142) or some other form of ornamentation, or else are semicircular, with an architrave and hood-mould or a complete entablature following the curve of the arch (Fig. 143).
In the latter case pilasters or small columns are also frequently employed to decorate them, finished with an entablature and pediment, enclosing a tympanum partaking of the features of the style in which the building is designed (see Fig. 143). The head is usually in one stone or, if jointed, built up on the principles illustrated in the page illustration of a mausoleum (Plate V.). In the latter case the arch is composed of voussoirs or arch stones radiating from the centre, the arch being always of semicircular form.