For the quick responses, thank you very much!
JewishGen Discussion Group digest wrote:
The Austrian Empire used
the Ferro Meridian, which passes through Hierro (or Ferro) Island, the
western-most of the Canary Islands. This makes sense for a European
power, as everything in Europe would have an East Longitude. Very
opportunity for that messy math connected with comparing points on both
sides of the Prime Meridian.
The Ferro Meridian is 17 degrees 40 minutes East of the Greenwich
Hence the difference you noted.
As I might have noticed, the upper left corner of each maplet reads
"ostlich v. ferro" which obviously (now) means "Eastward of Ferro!"
This has been an educational experience!
Steven B. Tesser,