"gemination" of martian canals

The purported "gemination" of martian canals was a phenomenon first noted and named (from the Italian geminazzione = "to become doubled") by Schiaparelli in 1879. In observing the canal he had named Nilus, stretching between Lunae Lacus and Ceraunius, he saw "... two tracks regular, uniform in appearance, and exactly parallel ..." By 1882, he had charted as many as 20 geminations. Observers such as Perrotin, Pickering, and Lowell provided confirmation, though by the early 1890s the consensus was growing that the geminations could be explained as an optical or psychological effect. See also canals of Mars.