CAMERARIUS

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was done in 1612 by Christoph Scheiner, who fully described his
method of solar observation in the Rosa Ursina (1630), demon-
strating very clearly and practically the advantages and dis-
advantages of using the camera, without a lens, with a single
convex lens, and with a telescopic combination of convex
object-glass and concave enlarging lens, the last arrangement
being mounted with an adjustable screen or tablet on an equa-
torial stand. Most of the earlier astronomical work was done
in a darkened room, but here we first find the dark chamber
constructed of wooden rods covered with cloth or paper, and
used separately to screen the observing-tablet.

Various writers on optics in the I7th century discussed the
principle of the simple dark chamber alone and with single or
compound lenscs, among them Jean Tarde (Les Astres de Borbon,
1623); Descartes, the pupil of Kepler (Dioptrique, 1637);
Bettinus (Apiaria 1645); A. Kircher (Ars Magna Lucis et
Umbrae, 1646); J. Hevelius (Selenographia; 1647); Schott
[(]Magia Universalis Naturae et Artis, 1674); C.F.M. Deschales
(Cursus, seu Mundus Mathematicus, 1674); Z.Traber (Nervus
Opticus, 1675), but their accounts are generally more interesting
theoretically than as recording progrcss in the practical use and
development of the instrument.

The earliest mention of the camera obscura in England is of
probably in Francis Bacon's De Augmentis Scientiarum, but it is
only as an illustration of the projected images showing better
on a white scrcen than on a black one. Sir H. Wotton's letter
of 1620, already noted, was not published till 1651 (Reliquiae
Wottonianae, p. 141), but in 1658 a description of Kepler's portable
tent camera for sketching, taken from it, was published in a work
called Graphice, or the most exceIlent Art of Painting, but no
mention is made of Kepler. In W. Oughtred's English edition
(1633) of the Récréations mathématiques (1627) of Jean Leurechon
("Henry van Etten") there is a quaint description, with
figures, of the simple dark chamber with aperture, and also of a
sort of tent with a lens in it and the projection on an inner wall
of the face of a man standing outside, The English translation
of Porta's Natural Magick was published in 1658.

Robert Boyle seems to have been the first to construct a box
camera with lens for viewing landscapes. It. is mentioned in his
essay On the Systematic or Cosmical Qualities of Things (ch. vi.),
written about 1570, as having been mnde several years before
and since imitated and improved. It could be extended or
shortened like a telescope. At one end of it paper was stretched,
and at the other a convex lens fitted in a hole, the image
being viewed through an aperture at the top of the box. Robert
Hooke, who was some time Boyle's assistant, described (Phil.
Trans., 1668, 3, p. 741) a camera lucida on the principle of the
magic lantern, in which the images of illuminated and inverted
objects were projected on any desired scale by means of a broad
convex lens through an aperture into a room where they were
viewed by the spectators. If the objects could not be inverted,
another lens was used for erecting the images. From Hooke's
Posthumous Works (1705), p. 127, we find that in one of the
Cutlerian lectures on Light delivered in 1680, he illustrated the
phenomena of vision by a darkened room, or perspcctive box,
of a peculiar pattern, the back part, with a ooncave white screen
at the end of it, being cylindrical and capable of being moved
in and out, while the fore part was conical, a double convex
lens being fixed in a hole in front, The image was viewed
through a large hole in the side. It. was between 4 and 5 ft.
long.

Johann Zahn, in his Oculur Artificialis Teledioptricus (1685 -
1686), described and figured two forms of portable box cameras
with lenses, One was a wooden box with a projecting tube in
which a combination of a concave with a convex lens was fitted,
for throwing an enlarged image upon the focusing screen,
which in its proportions and application is very similar to our
modem telephotographic objectives. The image was first thrown
upon an inclined mirror and then reflected upwards to a paper
screen on the lop of the box. In an earlier form the image is
thrown upon a vertical thin paper screen and viewed through a
hole in the back of the camera. There is a great deal of practical
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information on lenses in connexion with the camera and other
optical instruments, and the book is valuable as a repertory
of early practical optics, also for the numerous references to
and extracts from previous writers. An improved edition was
published in 1702.

Most of the writers already noticed worked out the problems
connected with the projection of images in the camera obscura
more by actual practice than by calculation, but William
Molyneux, of Dublin, seems to have been the first to treat them
mathematically in his Dioptrica Nova (1692), which was also the
frst work in English on the subject, and is otherwise an interest-
ing book. He has fully discussed the optical theory of the dark
chamher, with and without a lens, and its analogy to the eye.
[sic] also several optical problems relating to lenses of various forms
and their combinations for telescopic projection, rules for finding
foci, &c. He does not, however, mention the camera obscura
as an instrument in use, but in John Harris's Lexicon Technicum
(1704) we find that the camcra obscura with thei arrangement
called the "scioptric ball," and known as scioptricks, was on sale
in London, and after this must havebcen in common use as a
sketching instrument or as a show.

Sir Isaac Newton, in his Opticks (1704), explains the principle
of the camera obscura with single convex lens and its analogy
with vision in illustration of his seventh axiom, which aptly
embodies the correct solution of Aristotle's old problem. He
also made great use of the simple dark chamber for his optical
experiments with prisms, &c. Joseph Priestley (1772) mentions
the application of the solar microscope, both to the small and
portable and the large camera obscura. Many patterns of these
two forms for sketching and for viewing surrounding scenes
are described in W. J. 's Gravesande's Essai de perspective
(1711), Robert Smith's Compleat System of Optics (1738), Joseph
Harris's Treatise on Optics (1775), Charles Hutton's Philo-
sophical and Mathematical Dictionary, and other books on optics
and physics of that period. The camera obscura was first
applied to photography (q.v.) probably about 1794, by Thomas
Wedgevood. His experiments with Sir Humphrey Davy in
endeavouring to fix the images of natural objects as seen in the
camera were published in 1802. (Journ. Roy. lnst.). J. Wa.).

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