![Image](http://www.gbps.org.uk/boards/images/transferred/818_1.jpg)
I'm baffled by the rates shown on this 1781 letter from Liverpool to Lunga, Argyllshire. It's endorsed "pr Edinburgh and Inverary", so presumably it went from Liverpool to Berwick (via Ferrybridge) and then onwards as directed.
My reading of David Robinson's "for the port and carriage of letters" would suggest a rate of 4d Liverpool to Berwick, plus 2d Berwick to Edinburgh, plus 4d Edinburgh to destination. However the actual rates on the cover suggest otherwise. Any suggestions as to where I'm going wrong?