Ruskin defines the Arab School in Stones of Venice:
The Arab school is at first the same (as the Byzantine) in its principal features, the Byzantine workmen being employed by the caliphs; but the Arab rapidly introduces characters half Persepolitan, half Egyptian into the shafts and capitals: in his intense love of excitement he points the arch and writhes it into extravagant foliations; he banishes the animal imagery, and invents an ornamentation of his own (called Arabesque) to replace it: this not being adapted for covering large surfaces, he concentrates it on features of interest, and bars his surfaces with horizontal lines of colour, the expression of the level of the desert. He retains the dome and adds the minaret. All is done with exquisite refinement. (Works, 9.39)
It is not clear what distinctions, if any, Ruskin makes between what he calls Moorish (see House Book 2 p.13), Saracenic, and Arabic forms. See Notebook M p.48 for the ‘Saracenic’ arches of St Mark’s, which led to the ‘sharpening of the bend of the arch’ in Venice. At Notebook M2 p.132L Ruskin mentions Lindsay on the Saracenic influence on Cremona Duomo (for the ‘minarets’ of Cremona see here.
In Venice the 4th Order Window and arch is to be considered the true Arabic form (Notebook M2 p.2), and Notebook M p.37 refers to the ‘Casa d’Oro and such arabic work’. Ruskin’s indexes to M and M2 cite arches defined by Ruskin as Arabic at Notebook M2 p.72 and Bit Book pp.49-50 (Treasury Door at St. Marks); Gothic Book pp.60-62; Gothic Book p.65 (‘Arabic door in North Transept of St. Mark’s’, and on that see the reference at Notebook M p.198; House Book 2 p.12 and House Book 2 p.13).
There are frequent references to ‘arabesque’ ornament.
Implicit in all of them is the racial stereotyping which came easily to Ruskin and many of his contemporaries; see Notebook M p.76 on the ‘wild/restless’ Arab in the context of Ruskin’s fantasies in St Mark’s Square.
[Version 0.05: May 2008]