At the time, Hittorf and other scientists did not know about electrons
or the composition of atoms. The discovery of the cathode ray
was an important step toward understanding our universe.
Although we understand the electromagnetic spectrum,
which describes the range and limits of the behavior of photons,
we have yet to fully pry apart and control all particles.
Like photons, particles may travel.
Hence travelling electrons, neutrinos, and ions.
Hence electron and ion guns and particle accelerators.
See also in The book of science:
Readings on wikipedia: