In a treatise on astronomy, published a little after this in 1581, by Apian and Gemma Frison, they very distinctly state their belief in a round earth, though they do not go into details of its surface. The argument is the old one from eclipses, but the figures they give in illustration are very amusing, with three or four men of the size of the moon disporting themselves on the earth's surface. As, however, they all have their feet to the globe representing the earth, and consequently have their feet in opposite directions at the antipodes, the idea is very clearly shown. [Illustration: FIG. 36.] "If," they say, "the earth were square, its shadow on the moon would be square also. "If the earth were triangular, its shadow, during an eclipse of the moon, would also be triangular. [Illustration: FIG. 37.] "If the earth had six sides, its shadow would have the same figure. [Illustration: FIG. 38.] "Since, then, the shadow of the earth is round, it is a proof that the earth is round also." This of course is one of the proofs that would be employed in the present day for the same purpose. The most remarkable of all the fantastical systems, however, the _chef d'oeuvre_ of the cosmography of that age, was the famous system of the square earth, with solid walls for supporting the heavens. Its author was _Cosmas_, surnamed _Indicopleustes_ after his voyage to India and Ethiopia. He was at first a merchant, and afterwards a monk. He died in 550. His manuscript was entitled "Christian Topography," and was written in 535. It was with the object of refuting the opinions of those who gave a spherical form to the earth that Cosmas composed his work after the systems of the Church Fathers, and in opposition to the cosmography of the Gentiles. He reduced to a systematic form the opinions of the Fathers, and undertook to explain all the phenomena of the heavens in accordance with the Scriptures. In his first book he refutes the opinion of the sphericity of the earth, which he regarded as a heresy. In the second he expounds his own system, and the fifth to the ninth he devotes to the courses of the stars. This mongrel composition is a singular mixture of the doctrines of the Indians, Chaldeans, Greeks, and Christian Fathers.