Page 441 - 89 history of astronomy_opt

times with several umbrae in one penum-
bra. He has left us many drawings of these
spots, and he fixed their period of rotation
as a lunar month.
[Illustration: SOLAR SURFACE, As Pho-
tographed at the Royal Observatory, Green-
wich, showing sun-spots with umbrae, penum-
brae, and faculae.]
It is not certain whether Galileo, Fabri-
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