Classical Usage: I’m going to admit that it was more than just the above word that I didn’t understand about this passage. I’m pretty sure Melville is describing Pip’s preabandonment, bright, cheery self. But, beyond that, I’m not really sure what’s going on, you can be the judge. In the previous sentence he’s talking about a water droplet, or maybe it’s a diamond, I’m not really sure. “Then come out those fiery effulgences, infernally superb . . .” the paragraph then calls the diamond the crown jewel of Hell. It’s all a little disturbing, and weird.
Classically Mad Usage: I can tell you this, I will be using ‘effulgences’ in a much more down to earth way, no creepy devilish water diamonds for this girl. Nope, I prefer something more along the lines of “Even after ten years I still get happy little butterflies when I see the effulgences of my engagement ring.“