Sketch of the Great Pyramid [of Giza] with permanent lines for astronomical observations, by Joseph Jopling Sketch in pencil, projecting lines and angles onto the faces of the Great Pyramid [of Giza, Egypt] represented from above, to facilitate astronomical observations. Angles are noted. Enclosures from the correspondence between Joseph Jopling and Sir John Herschel of March 1860, removed from the letter HS/10/417. 1860