Visitors entering Canaletto in England at the Yale Center for British Art are confronted with two large canvases reunited for the first time in a century: a 1745–46 view of the Molo in Venice on Ascension Day (cat. 54, presumably painted in Venice), and a view of the Thames below Westminster on Lord Mayor’s Day a year or so later (cat. 23, painted in London). It is an instructive comparison that sets up the themes of style, subject matter, and patronage explored by this exhibition. The Venetian view features all of the mature vedutista’s familiar hallmarks, with its frontal portraits of the Serenissima’s civic landmarks balanced between expanses of bright blue skies and grayish green water crowded with ceremonial barges, elegant spectators, and working boats all passing at different paces and trajectories amid the flapping flags. We see nearly the same formula in the London picture, down to the gilded barges, to the extent that historians have read it as emblematic of English Whig patrons’ desire to stress the sister cities’ shared devotion to a mercantile ideal. That interpretation is strengthened by the discovery that the Thames view was likely commissioned to join the quartet of pictures George Garnier had...