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of its surface, which does not well reflect the
sun’s light; proving that it always turns the
same face to Jupiter, as is the case with our
moon. This fact had also been established
for Saturn’s fifth satellite, and may be true
for all satellites.
In 1826 Struve measured the diameters
of the four satellites, and found them to be
2,429, 2,180, 3,561, and 3,046 miles.
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