from Albertus Magnus, and
who was probably L.B. Alberti, to whom Porta also refers, but not in
this connexion.

G.B.I.T. Libri-Carucci dalla Sommaja (1803-1869), in his account of the
invention of the camera obscura in Italy (_Histoire des sciences
mathematiques en Italic_, iv. 303), makes no mention of Alberti, but
draws attention to an unpublished MS. of Leonardo da Vinci, which was
first noticed by Venturi in 1797, and has since been published in
facsimile in vol. ii. of J.G.F. Ravaisson-Mollien's reproductions of the
MSS. in the Institut de France at Paris (MS. _D_, fol. 8 _recto_). After
discussing the structure of the eye he gives an experiment in which the
appearance of the reversed images of outside objects on a piece of paper
held in front of a small hole in a darkened room, with their forms and
colours, is quite clearly described and explained with a diagram, as an
illustration of the phenomena of vision. Another similar passage is
quoted by Richter from folio 404b of the reproduction of the _Codice
Atlantico_, in Milan, published by the Italian government. These are
probably the earliest distinct accounts of the natural phenomena of the
camera obscura, but remained unpublished for some three centuries.
Leonardo also discussed the old Aristotelian problem of the rotundity of
the sun's image after passing through an angular aperture, but not so
successfully as Maurolycus. He has also given methods of measuring the
sun's distance by means of images thrown on screens through small
apertures. He was well acquainted with the use of magnifying glasses and
suggested a kind of telescope for viewing the moon, but does not seem to
have thought of applying a lens to the camera.

The first published account of the simple camera obscura was discovered
by Libri in a translation of the _Architecture_ of Vitruvius, with
commentary by Cesare Caesariano, one of the architects of Milan
cathedral, published at Conio in 1521, shortly after the death of
Leonardo, and some twenty years before Porta was born. He describes an
experiment made by a Benedictine monk and architect, Dom Papnutio or
Panuce, of the same kind as Leonardo's but without the demonstration.

About the same time Francesco Maurolico, or Maurolycus, the eminent
mathematician of Messina, in his _Theoremata de Lumine et Umbra_,
written in 1521, fully investigated the optical problems connected with
vision and the passage of rays of light through small apertures wit