is a profile of the line from Montgomery to Birmingham -- The South and
North RR, dated 1874. This image comes from the map archive at the
University of Alabama.
profile view is used in Civil Engineering to show a long alignment in a
short space. Thus, the vertical is greatly exaggerated. In
this drawing, the vertical is exaggerated over 300 times! So, the
railroad grades are not nearly as steep as they look.
require flat grades (rise per run) -- 1% is a pretty steep grade for a
railroad. That means that if the line rises 50 feet in one mile,
the grade is about 1%.
numbers on the slope are the grade in feet per mile, a common measure in
railroad engineering. Thus, the grade from Cahaba Mines Switch to
Brock's Gap was 54.6 feet per mile, or better than 1%.