ments of the same kind, but although Dr John Freind, in his
_History of Physick_, has given him the credit of the invention on the
strength of a passage in the _Perspectiva_, there is nothing to show
that he constructed any instrument of the kind. His arrangement of
concave and plane mirrors, by which the realistic images of objects
inside the house or in the street could be rendered visible though
intangible, there alluded to, may apply to a camera on Cardan's
principle or to a method of aerial projection by means of concave
mirrors, which Bacon was quite familiar with, and indeed was known long
before his time. On the strength of similar arrangements of lenses and
mirrors the invention of the camera obscura has also been claimed for
Leonard Digges, the author of _Pantometria_ (1571), who is said to have
constructed a telescope from information given in a book of Bacon's
experiments.

Archbishop Peckham, or Pisanus, in his _Perspectiva Communis_ (1279),
and Vitello, in his _Optics_ (1270), also attempted the solution of
Aristotle's problem, but unsuccessfully. Vitello's work is to a very
great extent based upon Alhazen and some of the earlier writers, and was
first published in 1535. A later edition was published, together with a
translation of Alhazen, by F. Risner in 1572.

The first practical step towards the development of the camera obscura
seems to have been made by the famous painter and architect, Leon
Battista Alberti, in 1437, contemporaneously with the invention of
printing. It is not clear, however, whether his invention was a camera
obscura or a show box, but in a fragment of an anonymous biography of
him, published in Muratori's _Rerum Italicarum Scriptores_ (xxv. 296),
quoted by Vasari, it is stated that he produced wonderfully painted
pictures, which were exhibited by him in some sort of small closed box
through a very small aperture, with great verisimilitude. These
demonstrations were of two kinds, one nocturnal, showing the moon and
bright stars, the other diurnal, for day scenes. This description seems
to refer to an arrangement of a transparent painting illuminated either
from the back or the front and the image projected through a hole on to
a white screen in a darkened room, as described by Porta (_Mag. Nat._
xvii. cap. 7) and figured by A. Kircher (_Ars Magna Lucis et Umbrae_),
who notes elsewhere that Porta had taken some arrangement of projecting
images from an Albertus, whom he distinguished