Ruskin’s Index at Notebook M p.221 reads:
Fondaco dei Turchi, Upper arcade, 49, 50
Lower 55 Generally, 56, 146, 159
The references in the index to the upper and lower arcades are contradicted by the text of M. The passage at Notebook M pp.49f (with reference to Sheet No. 31) is said there by Ruskin to be about the lower arcade, and Notebook M p.55 (with reference to Sheet No. 36 [n/a]) to be about the upper. Compare the ambiguous way in which the first version of the index in manuscript form presents the references to the arcades of the Fondaco dei Turchi at St M[arks] Book p.10. It seems likely that it is the ambiguity in that draft which caused the confusion in the index and that the description in the text is the correct one.
[Version 0.05: May 2008]