The passage above comes from Edward Gibbon's History of the Decline and Fall of the Roman Empire and concerns Julian the Apostate's failed attempt to rebuild the Jewish Temple. For much of Christianities history, the failure of this last pagan emperor to discredit scripture by attempting to contradict the word of Christ was seen as a miraculous vindication of the faith.
Two millennia later Gibbon, equipped with the tools of the Enlightenment, made perhaps the first secular analysis of an event earlier treated by Church historians with little scrutiny.
In the following excerpt he gives a more reasonable explanation that fits the accounts, and in the process reveals what a little time and knowledge of chemistry can do to bring down ancient perceptions:
It is a fact now popularly known, that when mines which have been long closed are opened, one of two things takes place; either the torches are extinguished and the men fall first into a swoon and soon die; or, if the air is inflammable, a little flame is seen to flicker round the lamp, which spreads and multiplies till the conflagration becomes general, is followed by an explosion, and kill all who are in the way. - G.
My intent in discussing the excerpt above and the footnote that follows it were not so much to display a great writer's powers of observation and irony so much as to display those qualities of the Enlightenment at work here in miniature.
Gibbon characterized himself as a “philosophic historian”. Much has been made of this title, which I won't go into depth about here, but briefly it is a change in the way in which historians did history. No longer were explanations for events to be sought for in the divine will or superstition, but evidence was to be judged and scrutinized without recourse to theology or fate. As with the birth of the sciences, explanation for phenomena were to be sought in nature and no longer simply passed over as mystery. For much these same reasons the writing of history would pass from the hands of educated gentlemen of leisure such as Gibbon, and become the sole province of the “specialist”.
Whether we have lost or gained by this arrangement I leave it up to the reader to decide.