parelli continued to study these curious phenomena, having them practically all to himself, Indeed, his grand isolation in the quest makes one of the finest and saddest chapters in the history of discovery. In the course of these solitary years he came to see the canals better, and they grew, on improving acquaintance, steadily more strange. He found that they were far more regular than he had at first thought, and he noted that they were dependent in appearance upon the season of the planet's year. So, likewise, were the large dark markings, and he attributed the behavior of both to a seasonal shift of water over the surface.
His theory of the planet's physical condition, derived from his observations, was as follows : that the polar caps were ice and snow ; that the blue-green areas were seas and the reddish-ochre ones land; that the canals were natural water-channels or straits honeycombing the land and cutting it up into a patchwork of large islands, a sort of natural Venice on a world-wide scale ; and finally that the surface was subject to annual or semiannual inundations and dryings-up, timed to the melting of the polar caps.
Schiaparelli retired practically in 1892, though not formally till a little later. His work was taken