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Mars, in 1869. In the 1877 opposition Schi-
aparelli revived interest in the planet by the
discovery of canals, uniformly about sixty
miles wide, running generally on great cir-
cles, some of them being three or four thou-
sand miles long. During the opposition of
1881-2 the same observer re-observed the
canals, and in twenty of them he found the
canals duplicated,[4] the second canal be-
510
