Description
Designed to aid chart work and replace parallel rulers. The straight edge is placed on the chart from departure point to destination, then moved to nearest meridian line when seen through hole in center of wheel. The wheel is turned until N lines up on the meridian line and the true course is indicated by the index line.
There is one on display in theNational Maritime Museum in Greenwich, England that is not as clean as this one. This Museum is the leading Maritime Museum in the UK, and may be the largest of its kind in the world. see it at http://www.nmm.ac.uk/collections/explore/object.cfm?ID=NAV0092
