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then, the centre of the earth is the point from which
distances must be measured to bodies attracted by the
earth. This was the first-fruit of his deduction.

From experiments executed before his time, Newton
knew the amount of the earth’s attraction at the earth’s sur-
face, or at a distance of 4,000 miles from its centre. His
object now was to measure the attraction at a greater dis-
tance, and thus to determine the law of its diminution.
But how was he to find a body at a sufficient distance?
He had no. balloon, and even if had, he knew that any height
which he could attain would be too small to enable him to
solve his problem. What did he do ? He fixed his thoughts
upon the moona—a body at a distance of 240,000 miles, or
sixty times the earth’s radius from the earth’s centre. He
virtually weighed the moon, and found that weight to be
g—gwth of what it would be at the earth’s surface. This is
exactly what his theory required. I will not dwell here upon
the pause of Newton after his first calculations, or speak of
his self-denial in withholding them, because they did not
quite agree‘with the observations then at his command.
Newton’s action in this matter is the normal action of the
scientific mind. If it were otherwise—if scientific men were
not accustomed to demand verification—if they were satis-
fied with the imperfect while the perfect is attainable, their
science, instead of being, as it is, a fortress of adamant,
would be a house of clay, ill-fitted to bear the bufl'etings of
the theologic storms to which it has been from time to time,
and is at present exposed.

Thus, we see, that Newton, like Torricelli, first pondered
his facts, illuminated them with persistent thought, and
finally divined the character of the force of gravitation. But
haviggcéhflsflmfledigfléfii $919119.principlethe.. had to re-
verse his steps, carrythe principle outward, and justify it
by demonstrating its fitness to external Nature. This he
did by determining the attraction of the earth and moon.

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