THE EARTH
“THE 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.”
[Illustration: The Earth]
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 be 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.
[Illustration: A Tower]
“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
perceiving 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.”
[Illustration: A Ship at Sea]
“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 next
morning?”
“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 me.”
“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
figure 6 followed by twenty-one zeros, or by 6 sextillions of
kilograms.”
“That number means nothing to me; it is too large,” Jules declared.
“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 Uncle Paul.
------------------------------------------------------------------------