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one
principal star, the center of the nebulous mass.
    By attentively watching, the observer would then have perceived
the other molecules of the mass, following the example of this
central star, become likewise condensed by gradually accelerated
rotation, and gravitating round it in the shape of innumerable stars.
Thus was formed the Nebulae , of which astronomers have reckoned
up nearly 5,000.
    Among these 5,000 nebulae there is one which has received the
name of the Milky Way, and which contains eighteen millions of
stars, each of which has become the center of a solar world.
    If the observer had then specially directed his attention to one
of the more humble and less brilliant of these stellar bodies,
a star of the fourth class, that which is arrogantly called the
Sun, all the phenomena to which the formation of the Universe is to
be ascribed would have been successively fulfilled before his eyes.
In fact, he would have perceived this sun, as yet in the gaseous
state, and composed of moving molecules, revolving round its axis
in order to accomplish its work of concentration. This motion,
faithful to the laws of mechanics, would have been accelerated
with the diminution of its volume; and a moment would have arrived
when the centrifugal force would have overpowered the centripetal,
which causes the molecules all to tend toward the center.
    Another phenomenon would now have passed before the observer's
eye, and the molecules situated on the plane of the equator,
escaping like a stone from a sling of which the cord had
suddenly snapped, would have formed around the sun sundry
concentric rings resembling that of Saturn. In their turn,
again, these rings of cosmical matter, excited by a rotary
motion about the central mass, would have been broken up and
decomposed into secondary nebulosities, that is to say,
into planets. Similarly he would have observed these planets
throw off one or more rings each, which became the origin of the
secondary bodies which we call satellites.
    Thus, then, advancing from atom to molecule, from molecule to
nebulous mass, from that to principal star, from star to sun,
from sun to planet, and hence to satellite, we have the whole
series of transformations undergone by the heavenly bodies
during the first days of the world.
    Now, of those attendant bodies which the sun maintains in their
elliptical orbits by the great law of gravitation, some few in
turn possess satellites. Uranus has eight, Saturn eight, Jupiter
four, Neptune possibly three, and the Earth one. This last, one
of the least important of the entire solar system, we call the
Moon; and it is she whom the daring genius of the Americans
professed their intention of conquering.
    The moon, by her comparative proximity, and the constantly
varying appearances produced by her several phases, has always
occupied a considerable share of the attention of the
inhabitants of the earth.
    From the time of Thales of Miletus, in the fifth century B.C.,
down to that of Copernicus in the fifteenth and Tycho Brahe in
the sixteenth century A.D., observations have been from time to
time carried on with more or less correctness, until in the
present day the altitudes of the lunar mountains have been
determined with exactitude. Galileo explained the phenomena of
the lunar light produced during certain of her phases by the
existence of mountains, to which he assigned a mean altitude of
27,000 feet. After him Hevelius, an astronomer of Dantzic,
reduced the highest elevations to 15,000 feet; but the
calculations of Riccioli brought them up again to 21,000 feet.
    At the close of the eighteenth century Herschel, armed with a powerful
telescope, considerably reduced the preceding measurements.
He assigned a height of 11,400 feet to the maximum elevations,
and reduced the mean of the different altitudes to little more
than 2,400 feet. But Herschel's calculations were in their turn
corrected by the observations of Halley, Nasmyth, Bianchini,
Gruithuysen, and others; but