Commentators on the Second Woe

William Brown Galloway, The Gate of Prophecy, Being the Revelation of Jesus Christ by St. John, Theologically and Historically Expounded, and Shown to Elucidate Various Prophecies of Isaiah, Ezekiel, Daniel, Zechariah & St. Paul. London, 1846. vol 2. See pp. 102-103.

The invention and the artillery which thus form so prominent an object in the history of the fall of the empire, are not omitted in the striking and expressive imagery of the vision. The artillery are aptly symbolized and named as lion-like and devouring "mouths" of the invading armies, out of which issued "fire, and smoke, and brimstone." The very elements of gunpowder are accurately expressed by these three words, not indeed in its dormant, but in its active state; in which the brimstone or sulphur acts merely subserviently as a means of procuring easy and rapid ignition, and the other two, which are the most important ingredients, resolve themselves into fire and an expansive vapour. The image is therefore sufficiently philosophical as well as popular.