Re-reading Verne's Journey to the Center of the Earth makes me think of how much freer a science-fiction writer could be, in an era when there was fae less systematic scientific knowledge about the Earth and the physical world. I'm reminded of how old sci-fi books could postulate that there were swamps and vegetation on the planet Venus (e.g. in Jack Lewis's Perelandra) because the planet was known to be cloudy, but not yet known to be extremely hot and inhospitable. Verne wants a vast underground cavern that's somehow brightly illuminated, and he needs to supply no better explanation than "electricity" and mysterious glow discharges powered by who the heck knows what mechanism. Verne can get away with being vague. These days his work would be torn to bits by a myriad "hard science fiction" nerds.
I daresay it's easier to write about magic.
~Χαρά
I made a typographical error in that last passage and I'm leaving it. ~Χαρά