If necessary, a little plaster is added, to tone down the inner protuberances.

The solidly embedded stonework alternates with the pure mortarwork, of which each fresh course receives its facing of tiny encrusted pebbles.

As the edifice is raised, the builder slopes the construction a little towards the centre and fashions the curve which will give the spherical shape.

We employ arched centrings to support the masonry of a dome while building: the Eumenes, more daring than we, erects her cupola without any scaffolding.
A round orifice is contrived at the summit; and, on this orifice, rises a funnelled mouthpiece built of pure cement.

It might be the graceful neck of some Etruscan vase.