...but sometimes multiple posts can't be avoided, I'm afraid.
Yesterday, while I was actually reading something totally unrelated, I stumbled over the mention of a report from 1922 by a member of the geological survey, called
"Origin of the Brown Mountain Lights". So I googled the title and found a scanned version of a reprint of the report from the early 1970s.
I guess, anyone who considers going to Brown Mountain to "see the light" should read this as a warning, because the poor man apparently wasted two weeks recording nothing but train and car headlights. At least that's what he states in his conclusion. But judge for yourselves:
http://pubs.usgs.gov/circ/1971/0646/report.pdf
Following an earlier investigation (1913), in which the cause of the lights was determined as "train headlights" after only a few days, there had been new speculations when the lights refused to take a break during a flooding in 1916, when all rail traffic had been suspended. Finally, in 1922, the geological survey sent another investigator, George R. Mansfield, to settle the matter once and for all.
While I do think that he was biased towards finding another, slightly more complex mundane explanation, there are a few interesting observations and descriptions in the report.
Btw., IMO, there doesn't really seem to be agreement on how the phenomenon can be defined, sometimes it's singular "the light", often plural "the lights", sometimes it has to be stationary, other times it should move to be considered the (or a) Brown mountain light and so on. Which I think could mean that there's indeed a lot of misinterpretation of mundane stuff going on.
The first description of a light, starting at the end of page 2, might be an indication why the investigators probably jumped to the conclusion of train headlights. I think it's not really a coincidence that Mansfield quotes it first:
"(...)seen just above the horizon almost every night (...) the light rises in a southeasterly direction from the point of observation just over the lower slope of Brown Mountain, first about 7:30 p.m. and again at 10 o'clock. It looks much like a toy fire balloon, a distinct ball, with no atmosphere about it. It is much smaller than the full moon, much larger than any star and very red. It rises in the far distance from beyond Brown Mountain, which is about 6 miles from Rattlesnake Knob, and after going up a short distance, wavers and goes out in less than 1 minute. It does not always appear in exactly the same place, but varies what must amount in the distance to several miles. The light is visible at all seasons, so Mr. Anderson Loven, an old and reliable resident testifies."
The nightly appearance at exact times makes the train explanation very likely, of course. Later on, Mansfield states that the given times can be correlated with trains going by in the distance. The question is why the lights should be above the horizon and colored red, though, but of course he has some explanations ready for this too (reflective air layers, mist or smoke particles etc.)
A second description is given on page 5. Some locals set out to determine the cause of the lights in early 1916 but "did not satisfactorily achieve their object":
"(...) about 11:52 his party saw two lights (floating globes), 'apparently about the size of ordinary street lamps (...) seen from the distance of about 1 mile, flash out among the trees on the east side of Brown Mountain about one-eighth of the distance down from the summit. These lights moved horizontally southeastward, floating in and out of the ravines, along the mountainside past a dead pine tree in Mr. Martin's line of sight for a distance estimated at 2 miles. Then they returned northwestward about half that distance, again passing the line of the dead tree. At 12:13 the lights disappeared as suddenly as they came.'"
Unfortunately, there's no mention of the color but the street lamp comparison might mean that it was more yellowish-white than red. This 20 minutes long observation is a bit harder to explain, and the main witness, Mr. Martin, who seems to have been quite a sceptic himself, apparently had a hard time to do so himself. He later seems to have gone so far as to resort to a "mirage" (which is improbable at night) or even a misinterpretation of a much closer and smaller lightsource, namely a firefly (reminds me of some forum reactions). I guess he just didn't want to sound like he was favoring a "supernatural explanation" and thereby expose himself to the ridicule. Interestingly, he seems to have objected to Mansfield's train-and-car-headlights conclusion by saying that Mansfield obviously hadn't seen the real "Brown Mountain Light".
A Colonel Harris, who als seems to have disagreed very much with the train headlights explanation, describes the light as follows:
"It is a pale white light, as one seen through a ground glass globe, and there is a faint, irregularly shaped halo around it. It is confined to a prescribed circle, appearing three or four times in quick succession, then disappearing for 20 minutes or half an hour, when it repeats within the same circle."
Another good but quite different description comes from a Professor W.G. Perry:
"We occupied a position on a high ridge. Across several intervening ridges rose Brown Mountain, some 8 miles away. After sunset we began to watch the Brown Mountain direction. Suddenly there blazed in the sky, apparently above the mountain, near one end of it, a steadily glowing ball of light. It appeared to be about 10° above the upper line of the mountain, blazed with a slightly yellow light, lasted about half a minute, and then abruptly disappeared. It was not unlike the "star" from a bursting sky rocket or Roman candle, though brighter.
(...)
Viewing the lights from a fixed position our estimate of their location was most inexact; the varying color (almost a white, yellowish, reddish) may have been due to mist in the atmosphere; the view of the lights was a direct one and not a reflection; there seemed to be no regularity in their time of appearance; they came suddenly into being, blazed steadily, and as suddenly disappeared; they appeared against the sky and not against the side of the mountain.
Others who have seen this phenomenon make very different reports of their observation; and some who have seen it several times report that they have seen it in varying fashion; sometimes the light appears stationary (as was uniformly the case when I saw it); sometimes it appears to move rapidly--upward, downward, horizontally."
The report then proceeds to detail the observations of Mansfield's own two week investigation. While he is quick to dismiss most of them as train or car headlights, some as bush fires etc., there is one observation which probably was a harder one to explain:
"The light on line 1, when viewed in the telescope of the alidade, was accompanied by one or two subordinate lights. Its position was unchanged throughout the evening, but it varied in brightness. At some times, for long periods, it was so dim that it was practically invisible to the naked eye, though it was faintly shown in the telescope. At other times it flared brightly, so that Joseph Loven pronounced it a true manifestation of the Brown Mountain light."
There's no mention of the actual duration of the observation but the words "throughout the evening" don't seem to fit at least the explanation of car or train lights. But even so, and although he had been told that the lights had probably been seen since before the Civil War, when there were no electric lights around, and although he states oddities like the seeming fact that whenever people camped out on the mountain to see if they could get a closer look at the lights, they just would't show up, in the end his conclusion is "nothing out of the ordinary, just headlights and bush fires".
It's really like a pocket version of Project Blue Book. In my opinion the whole investigation mainly had the objective of debunking the "mysterious air" that was building up around the lights. Science smiting superstion once again. IMO, like with Blue Book, this was not motivated by some deeper conspiracy, but only by his unwillingness to hurt his reputation as a scientist and, probably, by what he thought his peers expected from him: not to add further to the rumors and provide a "satisfactorily explanation" once and for all.
I would be interested to know how much of this report is still valid today, nearly a century later. Is it still true that whenever people are camping on Brown Mountain to see them from closer up, the lights won't show up? Seems unlikely. If anybody has inside knowledge, please share.