NavList:

I wrote: I can see what you’ve done Frank.  You’ve fed the mathematical formula for a Mercator projection into a curve sketching programme and overlaid it on the geometrical projection of a sphere onto a cylinder.  DaveP  

Further to my last post when I said I could see what you’d done Frank, now I’m not so sure.  I can see the significance of the yellow circles on the side of the cylinder, but I’m not sure of the significance of the yellow curves themselves.  Do the points along them actually mean anything, or are the curves there just to indicate which latitude the yellow circles represent?  Incidentally, I just looked in a table of meridional parts for the first time in my life and found that there are 119.81 of them between 59.30N and 60.30N showing that the scale of a Mercator chart at 60N is indeed twice that at the equator.  DaveP