768
Survey of Jerusalem (1864); Ordnance Survey of Sinai
Peninsula (1869); Plans and Photographs of Stonehenge
and of Turusachan in the Island of Lewis (1867); and
Notes on the Great Pyramid of Egypt and the Cubits
Used in Its Design (1869). In addition he oversaw the
production of a photographic facsimile of the Domes-
day Book or ancient record of the Survey of English
lands, ordered in 1086 by William the Conqueror. This
was the fi rst systematic geographic record in England.
Under his leadership, photography was an integral
component of mapping and surveying accomplished by
one of the nineteenth century’s most infl uential forces
for exploration.
Kathleen Howe
JANSSEN, PIERRE JULES CÉSAR
(1824–1907)
French astronomer, inventor, and photographer
Janssen studied the solar spectrum and developed a spec-
trohelioscope in 1868. In 1867 he concluded that water
vapor was present in the atmosphere of Mars. He also
discovered an unknown spectral line in the Sun in 1868
and later shared that information with Norman Lockyer,
who was credited with the discovery of helium. Janssen
was the fi rst to note the granular appearance of the Sun,
and published a monumental solar atlas in 1904. Jans-
sen taught Mathematics and Physics and was appointed
as correspondent to India to observe the total eclipse
of the Sun in 1868. His fi rst contribution to scientifi c
photography was proof, using a spectroscope, that the
solar prominences are gaseous. He also discovered the
chromospheres, a type of gaseous envelope of the Sun.
The French government appointed him director of the
Astrophysics Observatory in Meudon, France, where
he resided for about 30 years. Janssen studied mainly
the Sun, publishing an atlas with almost 6000 pictures
of its surface.
The convention of photography confronts Janssen
with the given world, with what one can fi nd in the real
world and what the camera may register in its fragmen-
tary vision of time and space. The photographer merely
decides when, where and how to do it, which seriously
limits the author in the possibilities of creation based
on some direct way of shaping the image. In a certain
sense, the images had always been there—the task of
Janssen is only to spot and register it, which does not
seem much. But the history of photography proves
that one can perform enormous tasks in this seemingly
narrow fi eld. For Janssen himself as a player in the
history of photography is photography a creative tool
that is composed of repeatedly undertaken attempts
at transgression, attempts of going beyond the urely
documentary relation between the image and its object.
Transgressing this basic feature of photography was for
Janssen a fascinating challenge.
Janssen was born in Paris, in 22 February 1824.
He became handicapped by a childhood. Pierre Jules
César Janssen studied mathematics and physics at the
faculty of sciences at the university of Paris. He taught
at the lyceum Charlemagne in 1853, and in the school
of architecture 1865-71, but his energies were mainly
devoted to various scientifi c missions entrusted to him
He became very quickly fascinated with the spectro-
scopic work of Gustav Kirchhoff and Robert Bunsen.
Under their infl uence, the young man began his search
on the solar spectrum in 1862 and showed in particular
that certain lines of the spectrum are due to the steam
of the Earth’s atmosphere. He studied the work of John
William Draper, who took a photograph of the moon
in 1840. His son, Henry Draper, later became the fi rst
person to photograph the Orion Nebula in 1880, which
was essentially the fi rst deep sky photograph.
In 1857–58, he worked in Peru on the determination
of the magnetic equator and in 1861–62 and 1864, he
studied telluric absorption in the solar spectrum in Italy
and Switzerland.
In 1867 he conducted optical and magnetic experi-
ments at the Azores, successfully observing both transits
of Venus, the fi rst in 1874 in Japan, and the second of
the 1882 transit at Oran in Algeria. He took part in a
long series of solar eclipse expeditions, e.g., to Trani
(1867), Guntoor (1868), Algiers (1870), Siam (1875),
the Caroline Islands (1883), and to Alcosebre in Spain
(1905).
At the Azores (1867) he examined magnetic and
topographical conditions. In 1868 Janssen went to India
to observe a total eclipse of the Sun. He was unable
to correlate certain lines in the solar spectrum with
wavelengths of any known elements. English scientist
Norman Lockyer made the same discovery of a new,
unknown element and reported it simultaneously to the
French Academy of Sciences.
An intrepid traveler in spite of his infi rmity, Janssen
traveled to Peru, Italy, Switzerland, Algeria (which he
reached in a balloon from Paris besieged by the Prussian
army in 1870) and fi nally to Guntur, India.
At this great Indian eclipse of 1868 he demonstrated
the gaseous nature of red prominence, and devised a
method of observing it under ordinary daylight condi-
tions. One main purpose of his spectroscopic inquiries
was to answer the question whether the Sun contained
oxygen or not. An indispensable preliminary was the
virtual elimination of oxygen-absorption in the Earth’s
atmosphere, and his bold project of establishing an
observatory on the top of Mont Blanc was prompted
by a perception of the advantages to be gained by re-