Vidi ego, quod fuerat quondam solidissima tellus
Esse fretum: vidi factas ex acquore terras;
Ovid, Metam, xv., 262.
"What once was solid ground I've seen to be a strait:
Lands I've seen made from out the sea."
HAD Ovid not let Pythagoras say this intentionally of the Earth he might be credited with having meant it for Mars. So startlingly apposite is its application to the history of Martian discovery. For the verse expresses to a presentment the course of man's acquaintance with that planet. A surface supposed at first partly land and sea; the land next seen to be seamed with straits; and lastly the sea made out to be land. Such is the history of the subject, and words could hardly have put the facts more neatly. 'Vidi ego, quod fuerat quondam solidissima tellus esse fretum' sounds like Schiaparelli's own announcement of the discovery of the canals. Indeed I venture to believe he would have made it had he chanced to remember the verse. 'Vidi factas ex acquore terras' certainly sums up what has since been found for the seas.
Three stages mark the course of Martian map-making from its beginning sixty-odd years ago to the present day. They constitute three epochs in the subject, which may be recognized distinctly in the chain of successive charts made of the surface of the planet from then till now. Such a series, however, is not for most people obtainable. Only to specialists is the evidence for or against any scientific belief present at any time in its entirety. Not only has the new evidence not had time to filter through the usual channels into general absorption, but