Canals on Mars

"Some people went so far as to propose the idea that the canals were irrigation canals built by a supposed intelligent civilization on Mars. Percival Lowell was a strong proponent of this view, pushing the idea much further than Schiaparelli, who for his part considered much of the detail on Lowell's drawings to be imaginary. Some observers drew maps in which dozens if not hundreds of canals were shown with an elaborate nomenclature for all of them. Some observers saw a phenomenon they called "gemination", or doubling - two parallel canals.

Other observers disputed the notion of canals. The gifted observer E. E. Barnard did not see them. In 1903, Joseph Edward Evans and Edward Maunder conducted visual experiments using schoolboy volunteers that demonstrated how the canals could arise as an optical illusion,[1] since when a poor quality telescope views an object with many point-like features (e.g. sunspots or craters) they 'appear' to join up to form lines...

During the oppositions of 1892 and 1894, seasonal color changes were reported. As the polar snows melted the adjacent seas appeared to overflow and spread out as far as the tropics, and were often seen to assume a distinctly green colour. The idea that Schiaparelli's canali were really irrigation canals made by intelligent beings, was first hinted at, and then adopted as the only intelligible explanation, by Lowell and a few others. Newspaper and magazine articles about Martian canals captured the public imagination."