121. Doublet Petzval-type Lens, c. 1850
Signed: 'Horne, Thornthwaite & Wood, / 123 Newgate St London.'.
Doublet Petzval-type lens of f4 with a focal length of 250 mm, consisting of an achromatic front component with convex surface to the front, and a rear component of one planoconcave and one biconvex lens separated by an air space, all set in a brass barrel with rack and pinion focusing. The maximum aperture is 55.
Length 150 mm, diameter 85 mm.
Inventory no. 79,809.