Correct, WS, it was a Ruhmkorff lamp, called that because it implemented Ruhmkorff's electomagnetic inductor, invented by him in 1857.

As my uncle made this remark, he took in one hand the Ruhmkorff coil
apparatus, which hung round his neck, and with the other he put the
electric current into communication with the worm of the lantern.
And a bright light at once illumined that dark and gloomy tunnel!
The effect was magical!
Hans, who carried the second apparatus, had it also put into
operation. This ingenious application of electricity to practical
purposes enabled us to move along by the light of an artificial day,
amid even the flow of the most inflammable and combustible gases. Jules Verne, A Journey To The Center Of The Earth

This was brand new technology at the time. The book was published in 1864, only seven years after Ruhmkorff's discovery.