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138 XI. THE ARCH MASONRY. 'CONSTRUCTION.
u smaller one, or a window, and the masonry type of the
Venetian Gothic window is consequently three-pieced, c2.
§ xvi. The reader knows already where a cusp is useful.
It is wanted, he will remember, to give weight to those side
stones, and draw them inwards against the thrust of the top
stone. Take one of the side stones of c2 out for a moment, as>,
at d. Now the proper place of the cusp upon it varies with
the weight which it bears or requires; but in practice this
nicety is rarely observed; the place of the cusp is almost always
determined by aesthetic considerations, and it is evident that
the variations in its place may be infinite. Consider the cusp
as a wave passing up the side stone from its bottom to its top;
then you will have the succession of forms from e to g (Plate
III.), with infinite degrees of transition from each to each;
but of which you may take e, / and g, as representing three
great families of cusped arches. Use e for your side stones,
and you have an arch as that at h below, which may be called
a down-cusped arch. Use / for the side stone, and you have
i, which may be called a mid-cusped arch. Use g, and you
have k, an up-cusped arch.
§ xvn. The reader will observe that I call the arch mid-
cusped, not when the cusped point is in the middle of the
curve of the arch, but when it is in the middle of the side
piece, and also that where the side pieces join the keystone
there will be a change, perhaps somewhat abrupt, in the curvature.
I have preferred to call the arch mid-cusped with respect
to its side piece than with respect to its own curve, because
the most beautiful Gothic arches in the world, those of the
Lombard Gothic, have, in all the instances I have examined,
a form more or less approximating to this mid-cusped one at
i (Plate III.), but having the curvature of the cusp carried
up into the keystone, as we shall see presently: where, however, the arch is built of many voussoirs, a mid-cusped arch
will mean one which has the point of the cusp midway between
its own base and apex.
The Gothic arch of Venice is almost invariably up-cusped,
| Title | The stones of Venice - 1 |
| Creator | Ruskin, John |
| Publisher | J. Wiley |
| Place of Publication | New York |
| Date | 1889 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000167 |
| Type | Books/Pamphlets |
| Transcript | 138 XI. THE ARCH MASONRY. 'CONSTRUCTION. u smaller one, or a window, and the masonry type of the Venetian Gothic window is consequently three-pieced, c2. § xvi. The reader knows already where a cusp is useful. It is wanted, he will remember, to give weight to those side stones, and draw them inwards against the thrust of the top stone. Take one of the side stones of c2 out for a moment, as>, at d. Now the proper place of the cusp upon it varies with the weight which it bears or requires; but in practice this nicety is rarely observed; the place of the cusp is almost always determined by aesthetic considerations, and it is evident that the variations in its place may be infinite. Consider the cusp as a wave passing up the side stone from its bottom to its top; then you will have the succession of forms from e to g (Plate III.), with infinite degrees of transition from each to each; but of which you may take e, / and g, as representing three great families of cusped arches. Use e for your side stones, and you have an arch as that at h below, which may be called a down-cusped arch. Use / for the side stone, and you have i, which may be called a mid-cusped arch. Use g, and you have k, an up-cusped arch. § xvn. The reader will observe that I call the arch mid- cusped, not when the cusped point is in the middle of the curve of the arch, but when it is in the middle of the side piece, and also that where the side pieces join the keystone there will be a change, perhaps somewhat abrupt, in the curvature. I have preferred to call the arch mid-cusped with respect to its side piece than with respect to its own curve, because the most beautiful Gothic arches in the world, those of the Lombard Gothic, have, in all the instances I have examined, a form more or less approximating to this mid-cusped one at i (Plate III.), but having the curvature of the cusp carried up into the keystone, as we shall see presently: where, however, the arch is built of many voussoirs, a mid-cusped arch will mean one which has the point of the cusp midway between its own base and apex. The Gothic arch of Venice is almost invariably up-cusped, |
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