[T]hese names may be regarded as a mere artifice… After all, we speak in a similar way of the seas of the Moon, knowing very well that they do not consist of liquid masses.
During the opposition of 1879, Schiaparelli refined his original map, noting some changes such as the apparent invasion of a bright area known as Libya by Syrtis Major. This encouraged him in his belief that Syrtis Major was a shallow sea which at times flooded the lands around. He drew in more canals and for the first time reported what he called a “gemination,” or doubling of one of these features. Of the reality of the canali, if not their exact nature, he was utterly convinced: “It is [as] impossible to doubt their existence as that of the Rhine on the surface of the Earth.”
So began the great canal controversy. Were the canali real? And if so, what were they? In an influential 1893 article, Schiaparelli maintained that Mars is a planet of seasonal change, with a temporary sea forming around the northern polar cap as it melted each spring. In support of his belief in aMartian atmosphere rich in water vapor he pointed to the spectroscopic observations of Hermann Vogel. The canals, he asserted, comprised “a true hydrographic system” and perhaps “the principal mechanism … by which water (and with it organic life) may be diffused over the arid surface of the planet.” As to their origin, he leaned toward a natural explanation:
[W]e are inclined to believe them to be produced by an evolution of the planet, just as on the Earth we have the English Channel and the Channel of Mozambique.
Their singular aspect, and their being drawn with absolute geometrical precision, as if they were the work of rule or compass, has led some to see in them the work of intelligent beings… I am very careful not to combat this supposition, which includes nothing impossible.