At Works, 9.330 and following Ruskin sets out his views on the definition of ‘niche’ - which appears to include tabernacle and aedicule - and on the questions raised by the use of niches in Gothic architecture.
At Works, 10.243 the niche is seen as characteristic of Gothic.
At Works, 12.198 and following he examines the differences between Northern and Southern Gothic niches.
Notebook M p.14 attempts to define the evolution of the Gothic niche from a Greek temple. The Baldacchino of St Ambrogio in Milan is seen as an example of the first expansion of the Greek temple into the Gothic niche. Ruskin at Notebook M p.14 refers to Notebook N p.35L where the idea is illustrated with diagrams.
In addition to St. Mark’s niches and the Ducal Palace niches, niches in Venice are referred to at:
Notebook M p.36 and Notebook M p.37; Notebook M p.38; Notebook M p.128 - Frari (for a photograph showing the niches of the Frari West Front see here).
Notebook M p.37 SS Giovanni e Paolo (for a photograph showing the niches of SS Giovanni e Paolo West Front see here).
Notebook M p.59 in Calle dei Giardini, where the reference seems inconsistent with the assertion at Works, 10.280-281 that the Ducal Palace is the only secular building in Venice to have niches.
Notebook M p.61 - questions date of dogtooth around niches
Notebook M p.63 - superimposed on door into court at San Gregorio
Notebook M p.210; House Book 2 p.33 - for the niches of the West Front of the church of Madonna dell’ Orto see here and here.
Notebook M2 p.23 and Notebook M2 p.26 on tombs in the church of SS Giovanni e Paolo
Outside Venice there are references, given roughly in the order the notes seem to have been made by Ruskin, at:
Notebook N p.13L - Amiens on which compare Works, 9.263, a note presumably made before the beginning of this tour;
Notebook M p.19; Notebook M p.206; Notebook M2 p.14backL - on the baseness of the niches of Milan cathedral.
Notebook M pp.23ff on the Scala monuments in Verona. For a study from Ruskin’s reference series of one of the niches of the tomb of Cansignorio, with the house behind mentioned at Notebook M2 p.128L, see here.
The Castelbarco tomb in Verona is in the form of a niche and at Notebook M2 p.118 is said to be full of extraordinary energy (see the illustration facing Works, 9.176).
Notebook N pp.57L and 57 - niche at the tower of Ezzelino in Padua
Notebook M2 p.136 Norman character of niche at Genoa Duomo. The niche is set above the lion in the south west angle of the cathedral. For the West Front see here.
Notebook M2 p.163 at Vienne Cathedral. For photographs of the cathedral of Saint-Maurice in Vienne see here.
Notebook M2 pp.172f - Lyon
[Version 0.05: May 2008]