Complex sentence: The American gauges converged as the advantages of equipment interchange became increasingly apparent; notably, the South's broad gauge was converted to be compatible with standard gauge over the course of two days beginning on 31 May 1886.
Split into simpler sentences: The American gauges converged as the advantages of equipment interchange became increasingly apparent. Notably, all the broad gauge track in the South was converted to standard gauge over the course of two days beginning on 31 May 1886.