The copper coated carbon electrodes must be adjusted to a predetermined – centered - position prior to creating the arc. The red knobbed positional bracket is in the down (out of the way) position.

This image shows the red knobbed bracket in up position creating the exact centered position necessary for the arc light to sent through the lens behind the electrodes.
The lens transmits the focused light to a slit then to the diffraction grating then to the viewer lens.

The electrodes are then adjusted to where they barely touch which when power is on an electric arc will be generated. The specs on the shield wall are due to flying hot/molten particles.

A ceramic boat containing the pulverized mineral sample is placed on the hearth in lowered position.

The boat is raised to about this position after the electric arc is generated.

The arc is initiated and the sample laden boat is slowly raised into the arc.

The sample is totally submerged in a bath of the hot (2000+F to 5000+F) electric arc.
Fumes exit out the chimney.
Normally, the electric arc cannot be seen because a flip door is closed.