View from the Window at Le Gras
1826 or 1827. The exact year is disputed and unresolved even at the holding institution: Helmut Gernsheim originally dated the plate to 1826, but accepted 1827 in the third edition of his own history after Harmant and Marillier argued for it in 1967. The Harry Ransom Center's own published materials use both years, sometimes on the same page. - Heliograph: bitumen of Judea, hardened by light and rinsed clear with a mixture of oil of lavender and white petroleum, on a polished pewter plate (tin alloyed with lead, with trace iron, copper and nickel)