Topic summary
Fishbelly rail
Extracted from the Wikipedia article Rail profile.
History
The earliest of these in general use were short, cast-iron fishbelly rails, named for their shape. Rails made from cast iron were brittle and broke easily. They could only be made in short lengths, which soon led to unevenness of the track. As rolling techniques improved, John Birkinshaw's 1820 patent introduced wrought iron in longer lengths, replaced cast iron, and contributed significantly to the explosive growth of railroads in the period 1825–40. The cross-section varied widely from one line to another, but were of three basic types, as shown in the diagram. The parallel cross-section which developed in later years was referred to as bullhead.