The extent of Ruskin's knowledge of Canaletto 's painting has been questioned. The painting of St Mark's 'from the Manfrini collection' referred to in MP I:197 cannot be traced and may never have existed as a work by Canaletto but the point that Ruskin makes is applied by Unrau to a picture in the Royal Collection Constable, revised Links, Giovanni Antonio Canal 1697-1768, No 33. For the lily capitals Canaletto, according to Unrau, Ruskin and St. Mark's, p.21, substitutes 'masses that look like hair curlers. The columns of the portico are badly misproportioned.' Miller and Millar, who seek to defend Canaletto against Ruskin, consider the same picture in the Royal Collection and describe its treatment of the southern corner of St. Mark's as perfunctory:
A dull row of thirteen openings is shown on the balustrade in place of the two groups of four divided by a broad central upright crowned by a finial; the weight of the four columns pressing down on the single supporting column and the bulk of the capitals on which they rest have been weakened; and the element of fantasy in the basilica has been lost.( Miller and Millar, Exhibition Catalogue, London: The Queen's Gallery, Canaletto, p 38)
The contrast between this picture in the Royal Collection and Plate 6 of Examples of the Architecture of Venice of 1851 (facing Works, 11.330) is striking: the plate of the Southern Portico might have been made 'against Canaletto'. It reveals obvious failings in the canaletto versiopn, and goes a long way towards justifying Ruskin's depreciation of Canaletto.
Similarly the ripples in A Regatta on The Grand Canal of 1740 may not be representative of Canaletto's best work, but are in fact made up of repetitive loops and curls of precisely the kind that Ruskin describes.