Honestly sounds like it was a hydrogen airship & some flights of fancy by the—not known for their intellectual rigor—local writers

The "flapping fins" and "two great mugs thrust out from each side" certainly seem like ailerons and ballast. And the mentions of it going at "a great rate of speed" sound like what happens to dirigibles when they get caught broadside in side drafts. What's interesting is the mention of a metal prow. Later dirigibles had docking tips and lightning rods on their noses, but a metal prow seems like it would cause a lot of issues with center of lift. My only guess is it was some kind of lifting surface and the entire craft was an aerostat and not a true lighter-than-air craft.

The great speed referred to for some in this article was estimated at 250mph. For someone in 1897 that might have just been shorthand for incomprehensibly fast. These accounts feel a lot more similar to the navy pilot accounts of the pill/cigar shaped craft they’ve been tracking, which are also capable of a rapid change in speed along a new vector.

I mean… they sound vaguely similar. Mostly though that’s because they’re both describing unknown airships moving in unexpected ways.

Or a bunch of hot air... in an enclosed space..