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HE earth is round, as proved by the following facts. When,
in order to reach the town he is journeying toward, a
traveler crosses a level plain where nothing intercepts his
view, from a certain distance the highest points of the
town, the summits of towers and steeples, are seen first.
From a lesser distance the spires of the steeples become
entirely visible, then the roofs of buildings themselves; so
that the view embraces a great number of objects, beginning
with the highest and ending with the lowest, as the distance
diminishes. The curvature of the ground is the cause of it."
Uncle Paul took a pencil and traced on paper the picture
that you see here; then he continued:
"To an observer at A the tower is quite invisible because
the curvature of the ground hides the view. To the observer
at B the upper half of the tower is visible, but the lower
half is still hidden. Finally, when the observer is at C he
can see the whole tower. It would not be thus if the earth
were flat. From
 any distance the whole of a tower would be
visible. Afar off, no doubt, it would he seen with less
clearness than near to, on account of the distance; but it
could be seen more or less well from top to bottom."
Here is another drawing of Uncle Paul's, representing two
spectators, A and B, who, placed at very different
distances, nevertheless see the tower from top to bottom on
a flat surface. He resumed his talk.
"On dry land it is rare to find a surface that in extent and
regularity is adapted to the observation I have just told
you about. Nearly always hills, ridges, or screens of
verdure intercept the view and prevent one's seeing the
gradual appearance, from summit to base, of the tower or
steeple that one is approaching. On the sea no obstacle bars
the view unless it be the convexity of the waters, which
follow the general curvature of the earth. It is,
accordingly, there especially that it is easy to study the
phenomena produced by the rounded form of the earth.
"When a ship coming from the open sea approaches the coast,
the first points of the shore visible to those on board are
the highest points, like the crests of mountains. Later the
tops of high towers come into sight; still later the edge of
the shore itself. In the same way an observer who witnesses
from the shore the arrival of a vessel begins by
per-  ceiving the tops of the masts, then the topsails, then the sails
next below, and finally the hull of the vessel. If the
vessel were departing from the shore, the observer would see
it gradually disappear and apparently plunge under the
water, all in inverse order; that is to say, the hull would
be first hidden from view, then the low sails, then the high
ones, and finally the top of the mainmast, which would be
the last to disappear. Four strokes of the pencil will make
you understand it."
"How large is the earth?" was the next question from Jules.
"The earth is forty million meters in circumference or
10,000 leagues, for a league measures four kilometers. To
encircle a round table, you take hold of hands, three, four,
or five of us. To encircle in the same manner the vast
bosom of the earth, it would take a chain of people about
equal to the whole population of France. A traveler able to
walk day after day at the rate of ten leagues a day, which
no one could do, would take three years to girdle the globe,
supposing it to be all land and no sea. But, where are the
hamstrings that could resist three years of such continual
fatigue, when a walk of ten leagues generally exhausts our
strength and makes it impossible for us to begin again the
 "The longest walk I ever took was to the pine woods, where
we went to look for the nest of the processionary
caterpillars, the day of the thunderstorm. How
many leagues did we go?"
"About four, two to go and two to come back."
"Only four leagues! All the same I was played out. At the
end I could hardly put one foot before the other. It would
take me, then, from seven to eight years to go round the
world, walking every day as far as my strength would let
"Your calculation is right."
"The earth then is a very large ball?"
"Yes, my friend, very large. Another example will help you
to understand it. Let us represent the terrestrial globe by
a ball of greater diameter than a man's height—by a ball
two meters in diameter; then, in correct proportion,
represent in relief on its surface some of the principal
mountains. The highest mountain in the world is Gaurisankar,
a part of the Himalaya chain, in central Asia. Its peaks
rise to a height of 8840 meters. Rarely are the clouds high
enough to crown its crest, and its base covers the extent of
an empire. Alas! what does man become, materially, in face
of such a prodigious colossus! Well, let us raise the giant
on our large ball representing the earth; do you know what
will be needed to represent it? A tiny little grain of sand
which would be lost between your fingers, a grain of sand
that would stand out in relief only a millimeter and a
third! The gigantic mountain that overwhelmed us with its
immensity is nothing when compared with the earth. The
highest mountain in
 Europe, Mont Blanc, whose height is 4810
meters, would be represented by a grain of sand half as
large as the other."
"When you told us of the roundness of the earth," put in
Claire, "I thought of the enormous mountains and deep
valleys, and asked myself how, with all these great
irregularities, the earth could nevertheless be round. I see
now that these irregularities are a mere nothing in
comparison with the immensity of the terrestrial ball."
"An orange is round in spite of the wrinkles in its skin. It
is the same with the earth: it is round in spite of the
irregularities of its surface; it is an enormous ball
sprinkled with grains of dust and sand proportioned to its
size, and these are mountains."
"What a big ball!" exclaimed Emile.
"To measure the circumference of the earth is not an easy
thing, you may be sure; and yet they have done more than
that: they have weighed the immense ball as if it were
possible to put it in a scale-pan with kilograms for
counterweights. Science, my dear children, has resources
demonstrating in all its grandeur the power of the human
mind. The immense ball has been weighed. How it was done
cannot be explained to you to-day. No scales were used, but
it was accomplished by the power of thought with which God
has endowed us, to solve, to His glory, the sublime enigma
of the universe; by the force of reason, for which the
burden of the earth is not too heavy. This burden is
expressed by the
fig-  ure 6 followed by twenty-one zeros, or
by 6 sextillions of kilograms."
"That number means nothing to me; it is too large," Jules
"That is the trouble with all large numbers. Let us get
around the difficulty. Suppose the earth placed on a car and
drawn on a surface like that of our roads. For such a load,
what should the team be? Let us put in front a million
horses; and in front of that row a second million; then a
third row, still of a million; a hundredth, finally a
thousandth. We shall thus have a team of a thousand millions
of horses, more than could be fed in all the pastures of the
world. And now start; apply the whip. Nothing would move, my
children; the power would be insufficient. To start the
colossal mass, it would need the united efforts of a hundred
millions of such teams!"
"I don't grasp it any better," said Jules.
"Nor I, it is so enormous," assented his uncle.
"Yes, enormous, Uncle."
"So that the mind gets lost in it," said Claire.
"That is what I wanted to make you acknowledge," concluded