This and the following lot, are two magnificent capricci, which can be dated, on stylistic grounds, to the late 1770s, or early 1780s, when Robert had achieved a masterly ease and fluency with large-scale landscape decorations.
Despite his acknowledged mastery as a painter of landscape, Robert was criticised by contemporaries, particularly Diderot, for his treatment of the human figure. From 1767 onward, Robert tried to address this perceived weakness by copying figures by his friend François Boucher, and incorporating variations on them in his own paintings; indeed, a group of 28 drawings by Robert of figures copied from Boucher was formerly in the collection of Georges Ryaux (sold, Christie's, New York, 10 January 1996, lot 216). The girl riding side-saddle on a mule at the centre of La fontaine à la vestale is a direct quotation from Boucher's well-known painting Journey to Market (c. 1732, Museum of Fine Arts, Springfield). Robert seems to have been especially drawn to this motif, as he repeated it in a number of other paintings and drawings, beginning in the early 1760s, including a chalk study that passed through the Bourgarel sale (Paris, 15-16 June 1922, lot 199), the large decoration The Return of the Cattle, dated 1773, and the circular overdoor The Ruins, dated 1777 (both Metropolitan Museum of Art, New York).