Geissler Tubes

Geissler tubes were made primarily at the end of the 19th century and into the 20th as curiosities. They came in a great variety of sizes, shapes, and colors.

From Wikipedia:

Geissler tubes were mass produced from the 1880s as entertainment devices, with various spherical chambers and decorative serpentine paths formed into the glass tube. When the tube was handled (the terminals were insulated) the shape of the plasma changed. Some tubes were very elaborate and complex in shape and would contain chambers within an outer casing. If these were spun at high speed a visual disk of color was seen due to persistence of vision. (Somewhat similar devices in the form of stationary globes are now produced and sold for personal amusement.) As an educational tool they are also used to demonstrate the movement of electrons and the principles of a vacuum.

Mike Harrison has some lovely examples here as well as an incredible amount of other fascinating things on his site like this sinister and creepy mercury arc rectifier!