Enlarged diagram on f68v2-f68v1?

[Jorge_Stolfi]

Note that this T-O map is anomalous: it has two quarters at top and a half-circle below.

Couldn't the author just turn it around? 

Perhaps... But the topic of Oresme's book Le livre du ciel et du monde was the creation of Heavens and Earth.  In that illustration, where he is shown presenting the book to some big shot, the circle has water in the bottom half, and land partly covered with forest on the top half -- just as in the Genesis story. 

All the best, --stolfi