Plain directions for obtaining photographic pictures upon waxed and albumenised paper and glass, by collodion and albumen : including a third edition of Le Gray's Treatise on photography, a description of the stereoscope and the manner of taking pictures suited for it : also, the process for copying microscopic objects, &c. (1852)
Heisch, Charles, editor, Le Gray, Gustave, 1820-1884. Nouveau traité théorique et pratique de photographie sur papier et sur verre. English · London : T. Willats · leaf 69
67 between which is equal to the interval between the eyes of the observer ; this interval is generally about 2\ inches. … Fig. 7. Fig. 7. A cone, having its axis perpendicular to the referent plane and its vertex towards the observer. Fig. 8. Fig 8. The frustum of a square pyramid; its axis perpendicular to the referent plane, and its base furthest from the eye. “ For the purposes of illustration I have employed only…
Photography · Collodion process
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
![An illustration from Medical zoology and mineralogy. Or, Illustrations and descriptions of the animals and minerals employed in medicine, and of the preparations derived from them; including also an account of animal and mineral poisons, with figures coloured from nature / [John Stephenson]. (1832)](https://img.insideoutlibrary.com/img/200/wellcome-wellcome_b22010932-355-3.webp)
