...be a concave hemisphere with a central globe whose shadow fell on the lines engraved on the concavity. This would resemble the Greek scapha, a semicircular concave dial, or hemicyclium, ascribed by Vitruvius to Berosus the Chaldean, 340 B. C.; this was long in use in Rome, and many have been discovered. It consisted of a semi-spherical horizontal basin with a style erected in such a manner that its ext...