whole of space to be full of this "star dust."
Far from pretending to know either what the
celestial crickets, or what the air-stones are, I
am concerned only to remark here that these
puzzles of the museums are at present universally
believed to fall from the skies, to be of celestial
origin, and to display the action of fire. Shooting-stars
may be air-stones, only there is not a
particle of evidence to prove it; and certainly
the fact is a startling one that the skies should
be at present deemed regions of intense cold,
out of which fall stones looking as if they had
come out of furnaces!

The notion of central heat appears to be supported
by all the descriptions of the movement
experienced by the light sleepers over a good
part of England on the morning of the sixth of
October. I was awoke by a sensation which
reminded me of a billow coming under me when
floating on my back on the sea; another observer
felt as if a great beast were rousing himself up
under his large iron bedstead; and each of the
lads of a college suspected the others of getting
under their beds and shoving them up, or of
conspiring to shake the whole building. Many
persons describe a rising and sinking, or an
"uprising," and then a "setting." From the
comparatively slight and gentle character of this
earth billow, the direction of the movement has
not been marked by unmistakable signs, but it
appeared to be from north-west to south-east.
There is, of course, a difference in earth
billows, which is due to the strata upon which
the observer resides. I experienced the earthquake
of 1816 when residing upon granite rocks,
and was awoke, not by the earth wave, but by
the shaking of the granite walls of the house,
and the rattling of everything in it. Hugh
Miller, of Cromerty, has recorded that this earthquake
slewed partially round the blocks of a
granite obelisk, thus, in his neighbourhood,
registering its own course.

The crust of the Earth being elastic, and
holding in a sea of fire as the phenomena of
terrestrial heat, of hot springs, and of volcanic
eruptions, seem to prove risings and sinkings
would be natural consequences and constant
proofs of the structure supposed by the savans.
Travellers in Iceland boil sheep in the hot springs,
and certainly there is something whimsically
sublime in the notion of cooking one's boiled
mutton in water heated by the central heat of a
crusted sun! The suppositions of Buffon and
La Place, as we have seen, were very similar.
La Place supposed that the matter of the Sun
was once extended over all the space now occupied
by the planets, which were formed by the
contracting and cooling of portions of it.
Buffon tested these ideas by strange experiments
and calculations, obtaining singular results.
Buffon set up great furnaces near Montbard,
into which he put balls or bullets of iron,
copper, and minerals, as like as possible to those
composing the crust of the globe. These large
balls he heated up to the degree in which he
supposed the Earth was at first, and then
watched the time they took in cooling. Applying
the ratios arrived at in these ways, he
reckoned that from the incandescence of the
Earth to his time a period of seventy-five thousand
years had elapsed; life he calculated had
existed upon the globe thirty-five thousand
years; and the future duration of life upon it
could not, he concluded, exceed ninety-three
thousand years. The fauna and flora would
then die of cold. As Buffon himself grew old,
this theory of the duration of the Earth seemed
more natural to him, for growing old is growing
cold, and cold is death. But Fourier, the author
of the Mathematical Theory of Heat, took
Buffon up on his own ground, and by refuting
him, drove away his uncomfortable hypothesis.
He accepted as proved the notion of a central
sea of fire: and did not deny the alleged thinness
of the crust. There are then two oceans
of heat; the sea of solar heat above our heads,
and the sea of terrestrial heat under our feet.
Buffon, according to Fourier, erred when he
supposed that the cooling was still going on at
the rate at which it began. The central furnace
is still immense; but if its influence were to
cease to be perceptible or calculable altogether,
the planets and animals would only lose the benefit
of one-thirtieth of a degree of heat. The
cooling, then, has almost done its worst. The
Earth will not, some ninety thousand years
hence, die of old age! Of course we are all
glad to hear it, even for the sake of our descendants
a million generations after us!

An elastic shell, full of fire and liable to uprising
and sinking, three-fourths water and
one-fourth land at the surface, might be expected
to show its instability by displacing the water.
The water would flow from the upheavings and
into the hollows. Now this is just what we find.
All of the present land has been under the sea.
Nobody who knows the weaknesses of learned
men can be ignorant of their dislike to say, "I
don't know;" when, therefore, marine shells or
fossils were found on the tops of mountains, the
mediæval schoolmen called them freaks of
nature. Yet the geographers, philosophers, and
poets of antiquity— Strabo, Seneca, Plato, and
Ovid— knew their marine character. What Ovid
says in the fifteenth book of his Metamorphoses
on this subject is very curious. He had seen
what was formerly very solid land become a
firth; he had seen formed land arise out of the
water; he had seen marine shells strewn far
from any coast, and a rusty anchor upon mountain-tops;
what was a field, become a valley of
flowing water; and a hill drawn out of the
water of a morass.

Bernard de Palissy, the potter, who knew
neither Greek nor Latin, opened a course of three
lectures in Paris, to prove, by comparing specimens,
that the fossil shells were identical with
the marine shells of the present epoch. This
course was opened the year before young Francis
Bacon arrived in Paris as an attaché to the
English Embassy. During the three years he
remained in France, Bacon must have heard of
this refutation of one of the statements of the
schoolmen, for the most eminent medical men of