sound as it passed, or bounce of an explosion were
heard.

"It may deserve the honorable society's thoughts,
how so great a quantity of vapor should be raised to
the top of the atmosphere, and there collected, so
as upon its ascension or otherwise illumination, to
give a light to a circle of above one hundred miles
diameter, not much inferior to the light of the moon;
so as one might see to take a pin from the ground in
the otherwise dark night. 'Tis hard to conceive what
sort of exhalations should rise from the earth, either
by the action of the sun or subterranean heat, so as to
surmount the extreme cold and rareness of the air in
those upper regions: but the fact is indisputable, and
therefore requires a solution."

From this much of the paper it appears that there
was a general belief that this burning mass was
heated vapor thrown off from the earth in some
mysterious manner, yet this is unsatisfactory to Halley,
for after citing various other meteors that
have appeared within his knowledge, he goes on to
say:

"What sort of substance it must be, that could
be so impelled and ignited at the same time; there
being no Vulcano or other Spiraculum of subterraneous
fire in the northeast parts of the world, that
we ever yet heard of, from whence it might be projected.