re than this, the enquiry would be useless
to us in our Venetian studies, where the roofs are either not
contemporary with the buildings, or flat, or else vaults of the simplest
possible constructions, which have been admirably explained by Willis in
his "Architecture of the Middle Ages," Chap. VII., to which I may refer
the reader for all that it would be well for him to know respecting the
connexion of the different parts of the vault with the shafts. He would
also do well to read the passages on Tudor vaulting, pp. 185-193, in Mr.
Garbett's rudimentary Treatise on Design, before alluded to.[50] I shall
content myself therefore with noting one or two points on which neither
writer has had occasion to touch, respecting the Roof Mask.

Sec. III. It was said in Sec. V. of Chapter III. that we should not have
occasion, in speaking of roof construction, to add materially to the
forms then suggested. The forms which we have to add are only those
resulting from the other curves of the arch developed in the last
chapter; that is to say, the various eastern domes and cupolas arising
out of the revolution of the horseshoe and ogee curves, together with
the well-known Chinese concave roof. All these forms are of course
purely decorative, the bulging outline, or concave surface, being of no
more use, or rather of less, in throwing off snow or rain, than the
ordinary spire and gable; and it is rather curious, therefore, that all
of them, on a small scale, should have obtained so extensive use in
Germany and Switzerland, their native climate being that of the east,
where their purpose seems rather to concentrate light upon their orbed
surfaces. I much doubt their applicability, on a large scale, to
architecture of any admirable dignity; their chief charm is, to the
European eye, that of strangeness; and it seems to me possible that in
the east the bulging form may be also delightful, from the idea of its
enclosing a volume of cool air. I enjoy them in St. Mark's, chiefly
because they increase the fantastic and unreal character of St. Mark's
Place; and because they appear to sympathise with an expression,
common, I think, to all the buildings of that group, of a natural
buoyancy, as if they floated in the air or on the surface of the sea.
But, assuredly, they are not features to be recommended for
imitation.[51]

Sec. IV. One form, closely connected with the Chinese concave, is,
however, often constructively right,--the gable with