As the proud owner of an old Maltese cross and a Paddle wheel tube I can attest to the beauty of these things. They also have significant value these days.
The glow in the tubes is produce both by florescence the soda glass (green) and the remaining gas molecules in the tube violet. They need some gas molecules to work as they are cold cathode.
Just going around your photo...
Top left is an Anode ray tube (actually positively charged ions in the less than perfect vacuum).
Bottom left is an X-ray tube (cold cathode, Rontgen type).
Center is a tube that demonstrates the heating effect of an electron beam (on the suspended foil target), it looks as if it's seen some use! Top right is a magnetic deflection tube, the white florescent screen shows the bending of the electrons' path when a magnet is held near it (there were also similar tubes with electostatic deflection plates.
Finally, bottom right is the Maltese cross tube, the cross is hinged, when up it shows a shadow as electrons are stopped by the cross (proving that they move in straight lines). When down, the previously shadowed portion of the end of the tube. The glow is produced by bombardment of the glass by the electron beam (well, unfocussed stream). The shadowed area doesn't get as much exposure so glows brighter when it is exposed.
A few cautions:
- The tubes are evacuated (as near as makes no difference) and thin individually hand-blown glass (not like mass produced CRTs). One of mine has a section of fingerprint in the glass (ouch!) and the other, a bubble in the glass. If you knock them against each other, a hard object, or stress them, they WILL implode with fast moving shards of glass flying in all directions.
- They are only intended for minimal current, they would have been driven by an induction coil, I drive mine at no more than 5kV with a current limit resistor to limit to a few hundred uA max. Too much current and you will overheat the electrodes.
- All of the tubes are capable of generating X-rays to some extent if driven at too high a voltage - particularly the X-ray tube (obviously). They produce soft X-rays many of which are absorbed by flesh rather than passing through.
In terms of age, they are notoriously difficult to age but looking at the detail and stands, some of them could be 1920s. They are still manufactured to this day in Germany.
A really nice collection! I wish I could complete mine. Handle with care!
P.S. Oops, some duplication with ceoxrad's and NottheDan's replies while typing.