What is a conflagration? (From Stevenson's Dr. Jekyll and Mr. Hyde)

A large disastrous fire.

. . . for here it would be dark like the back-end of evening; and there would be a glow of a rich, lurid brown, like the light of some strange conflagration; and here, for a moment, the fog would be quite broken up, and a haggard shaft of daylight would glance in between the swirling wreaths.

From Stevenson's Dr. Jekyll and Mr. Hyde.