Which way ran ancient meridian 0°, called the Ferro Meridian?

ElHierro- the smallest island in the Spanish archipelago of the Canary Islands. It is put farthest to the South and west in the archipelago. For centuries putting the island was recognised as a point of reference for deleting of maps and doing calculations.In 1634 XIII Louis of for Franko and Richelieu confirmed that the Ferro meridian should be used on maps as the meridian of the reference.