The reference is to the canopy over the golden altar of S. Ambrogio. Tourist guide books, in Ruskin’s time as now, saw the altar as a major feature of the city and the church. For Hahn (1999) the altar provides the ‘liturgical focus and spiritual center of the archiepiscopal city’. She provides a detailed account of its history, functions and iconography. However, Ruskin at Notebook M p.14 is precisely focused on the evidence its baldacchino offers on the relationship between the classical style and Gothic to the exclusion of any other consideration.
Compare the image at Notebook N p.35L with the photograph here and with the photograph below:
The use of the term ‘baldacchino’ is sometimes challenged in this context and ‘ciborium’ is preferred (as it is by O.E.D.). The reason is that ‘baldacchino’ is connected in its etymology with a woven silk brocade, and so should be used only of moveable canopies not stone structures. However it seems difficult to maintain this distinction in view of the routine use of the word ‘baldacchino’ in the context of the structure above the high altar of St. Peter's, Rome.
[Version 0.05: May 2008]