Question regarding track diagrams

[NW Mailing List]

First let me thank all of you for your wealth of knowledge and the generosity in sharing it in this forum. 

In N&W track diagrams from the early years, the ones with track layout at the bottom and curvature above that, there is a line that contains crosshatching, solid bars, diamonds, or the like. I assume this is to designate the type of ballast or rail bed construction. 

Is there a legend or standard for such designations and is it standard throughout the industry or specific to N&W?

Thanks,
Derek Shirley