It was quite natural that astronomers, the most conservative of all classes of observers, should have doubted the first announcement of Schiaparelli of the startling discovery of the _canali_ marking the face of the planet, the more so as year after year went by and yet with the utmost efforts of astronomers nothing of the nature of Schiaparelli's lines could be seen. What added greatly to the doubt about the lines, and at the same time strengthened the idea that the lines were illusory, was the subsequent announcement by Schiaparelli--undeterred by the universal skepticism--that at times the lines appeared double. What more convincing evidence could be offered than that the phenomenon was purely subjective? A few astronomers expressed their doubts in a courteous though hesitating manner. Professor Young, in his valuable text-book, "Elements of Astronomy" (1890), in correctly reporting Schiaparelli's discovery says: "He is so careful and experienced an observer that his results cannot be lightly rejected; and yet it is not easy to banish a vague suspicion of some error or illusion, partly because his observations have thus far received so little confirmation from others, and partly because his 'canals' are so difficult to explain. They can hardly be _rivers_, because they are quite straight; nor can they be _artificial_ water-ways since the narrowest of them are forty or fifty miles wide. To add to the mystery, he finds that at certain times many of them become _doubled_,--the two which replace the former single one running parallel to each other for hundreds, and sometimes thousands, of miles, with a space of 200 or 300 miles between them. He thinks that this _gemination_ of the canals follows the course of the planet's seasons."