X-ray print of the hand of Mr. H.A. Bumstead, 1896
YPM 1.161
Taken by A.W. Wright

Vacuum technology also improved in the 19th century, mainly through the work of William Crookes, who developed the Crookes' Tube.

Physicists had long known that the inside of a vacuum tube would glow when an electric current passed through it. In 1895 Wilhelm Röntgen connected a Ruhmkorff induction coil to a Crookes’ Tube and discovered that any fluorescent material outside the tube would also glow. Knowing that whatever was emanating from the tube was not light, he simply called these rays “X.”

After much experimenting, Röntgen placed a photographic plate between the tube and the fluorescent material and asked his wife to put her hand in front of the plate, thereby creating the first X-ray of a human hand. Within a few months physicists at Yale University replicated the experiment, and produced a series of X-ray plates. Some of these plates are displayed in the exhibit.

Railroad Tube with enlarged detail showing interior wheel
YPM 5.201
Maker and date unknown

The vacuum tube contributed to another famous and very important discovery. Crookes had already found that the glow inside a vacuum tube could be bent with a magnetic field. In 1897 Joseph John Thomson studied this phenomenon and concluded that the glow was caused by charged particles.

Thomson soon discovered that these particles, later named “electrons,” had mass and momentum. Momentum can be demonstrated using a Railway Tube: the electrons, which emanate from the cathode (or negative end) of the tube, move towards the anode (the positive end), hit the paddles and push the wheel along the tracks.