"X rays," also known as "Röntgen rays," were discovered only
eight or nine years before the time represented in Ulysses.
They seized the imagination of ordinary people like Bloom,
whose thoughts on the subject seem more than usually fuzzy.
In 1895 Wilhelm Röntgen, who held the physics chair at
Würtzburg University in Germany, was working with a
cathode-ray tube in his laboratory. He found that some kind of
radiation was exciting fluorescent materials far removed from
the tube (cathode rays were known to travel only a few
centimeters in air). He blocked the tube with heavy cardboard
and ensured that no light was entering the room, but the
fluorescence was not abated. With further experiments, he
found that the mysterious rays could penetrate many opaque
materials including human flesh, but could not penetrate far
into denser materials like metal and bone. He also found that
they could produce images on photographic plates.
Several days before Christmas in the same year, Röntgen used
his cathode-ray apparatus to take a radiographic image of his
wife Bertha's hand. Several days after Christmas, he submitted
an article describing his findings, along with the picture, to
a scholarly journal. The article excited widespread interest,
the picture became famous, and Röntgen won a Nobel prize in
1901. He named his mysterious findings X-rays, but much of the
world called them Röntgen rays. Their diagnostic potential was
recognized immediately: in 1896 a number of physicians and
surgeons used the new rays to look inside patients' bodies,
and at least two medical handbooks, Practical Radiography
and The X-ray, or, Photography of the Invisible and its
Value in Surgery, were published.
For more details of this story, see Dean Zollman's 2015 blog
"Wonders of the X-ray" at kimrendfeld.wordpress.com,
summarizing an article that was published in the American
Journal of Roentgenology in 1931, and "History of
Radiography," another blog on the NDT Resource Center at
www.nde-ed.org.
In Lestrygonians, a chapter concerned with the human
alimentary canal, Bloom walks along Duke Street "toward Dawson
street, his tongue brushing his teeth smooth" after his lunch
in Davy Byrne's pub. The narrative finds him in the middle of
an obscure train of thoughts: "Something green it would
have to be: spinach, say. Then with those Röntgen rays
searchlight you could." It is not at all clear why he
thinks that green objects would show up better than others
under X-rays (they do not, of course).
In Eumaeus the reader is treated to another display
of obscure reasoning when Bloom tries to persuade Stephen that
human intelligence can be attributed to "convolutions of the
grey matter" rather than to the actions of an immortal soul: "Otherwise
we would never have such inventions as X rays, for instance."
The bizarre logic seems to be that only intelligence produced
in a scientifically comprehensible way could possibly produce
scientific discoveries.
