CHAPTER I.
EARLY OBSERVERS OF MARS, -- Mars the only planet the surface of which is distinctly visible -- Early observation of the snow-caps and seas -- The 'canals' seen by Schiaparelli in 1877 -- Double canals first seen in 1881 -- Round spots at intersection of canals seen by Pickering in 1892 -- Confirmed by Lowell in 1894 -- Changes of colour seen in 1892 and 1894 -- Existence of seas doubted by Pickering and Barnard in 1894..