1205
have received some training from artist Francisco Cano
but was primarily self-taught. He worked in partnership
with his brother Horacio until 1897, after which he con-
tinued on his own. Although the Colombian coffee in-
dustry grew signifi cantly during his lifetime and brought
prosperity to the Medellín area, in general Rodríguez
struggled to support his wife and nine children, three of
whom later worked with him in the studio.
His images recorded a variety of subjects in both
studio portraits of individuals and groups and in outside
views. He photographed modern developments such as
railroads, trolleys and automobiles; urban monuments,
buildings and events; rural scenes, locations and people,
and ethnographic “tipos.” He is remembered for record-
ing the opening of the Amaga Railroad line in 1914.
Rodríguez was passionate about his craft, painted
his own backdrops and for several years kept a diary
in which he recorded his attempts to develop his skills
and abilities as a photographer. He received a number of
local awards for his work and in 1895 received a silver
medal at a New York show sponsored by the photogra-
phy journal, Light and Shadow. The image was that of
“Los Zapateros” (“The Cobblers”). His archive of over
two hundred thousand negatives is considered the of-
fi cial record of the Province of Antioquia during the fi rst
half of the twentieth century. The archive is preserved
in Medellín at the Biblioteca Pública Piloto.
Yolanda Retter Vargas
ROENTGEN, WILHELM (1845–1923)
Wilhelm Roentgen wrote or co-wrote fi fty-eight scien-
tifi c papers, but only the three he published on X-rays,
which he discovered and named, are now well known.
Among other subjects he investigated were the ratio of
the specifi c heat of gases, the polarisation of light in
gases, pyroelectricity and piezoelectricity, refractive
indices of fl uids, and the compression of liquids and
solids. At the time of his discovery of X-rays in 1895,
he was looking at electrical discharges through gases
at low pressure.
Roentgen began studying cathode rays generated in
a Crookes tube in the autumn of 1895. To detect them,
he used paper coated with barium platinocyanide, which
fl uoresces when struck by cathode rays. On 8 Novem-
ber 1895 he noticed that one of the sheets, lying some
distance away from the covered tube, was glowing.
Photographic plates fogged in similar circumstances had
been observed previously, but Roentgen was the fi rst to
investigate further. Since the range of cathode rays in air
had been shown to be only a few centimetres, he deduced
that the glow must be caused by some other form of ray.
Placing his hand in the path of the rays caused the outline
of his bones to appear on the coated paper.
X-rays are produced when cathode rays strike the
wall of the tube and Roentgen experimented with a
range of materials to determine their properties. He
found that interposing materials varying in density af-
fected the brightness of the rays by different amounts.
A magnetic fi eld did not defl ect them as it did cathode
rays but neither did they exhibit refl ection, refraction or
polarisation. It was because of these unusual character-
istics that Roentgen characterised them as “X-rays,” X
standing for unknown as he could not determine their
nature, although they were soon also known as Roentgen
rays in his honour. The theory behind the phenomenon
was unclear to him—he thought that they might be lon-
gitudinal vibrations in the ether. Later research showed
that they were electromagnetic waves with a very short
wavelength.
On 22 December 1895 he took the emblematic im-
age of his wife’s hand wearing a ring. He sent a paper
entitled On a New Kind of Ray to the Würzburg Physi-
cal-Medical Society six days later and on New Year’s
Day 1896 sent copies, with samples of X-ray images, to
a number of European colleagues. The story was pub-
lished in Vienna on 5 January and was soon widely dis-
seminated, bringing Roentgen instant fame. He followed
his fi rst paper with two more, in March 1896 and May
1897, which mapped the properties of the new ray.
The phenomenon was easily replicated, with unam-
biguous results; and unlike the increasingly abstruse
details of laboratory science, the results were obvious
to the layperson. Popular international interest too
was immediate and paralleled scientifi c dissemination
through the academic press. Awareness was stimulated
by reproductions in illustrated magazines of X-ray
images of a wide range of objects. They became the
subject of an enormous quantity of commentaries as
well as fi ction, poetry and cartoons, though the satirical
edge of many betrayed fears over loss of privacy and
possible immorality.
The nature of X-rays raised the diffi culty of fi tting
them into a conceptual framework, hence the align-
ment with photography which, despite the efforts of a
number of early commentators to point out the obvious
differences, glossed over the method by which each
was achieved. As the images created by X-rays could
be recorded on photographic plates, it was a natural as-
sumption that they shared other characteristics. X-rays
were seen as analogous to photography except that they
captured information not visible to the naked eye.
Despite these differences the label “New Photog-
raphy” caught on quickly, and had a certain validity.
Photography had already extended the capabilities
of perception, with its ability to freeze motion, take
images of stars invisible to the naked eye and record
microscopic organisms. At the same time Roentgen
was announcing his discovery, moving images, which
could reproduce motion, were being projected for the