Complex sentence: By 1899, the first batch of six locomotives of the Midland System was no longer reflected in the locomotive register and, by 1904, all six of the Eastern System were gone from the register as well.
Split into simpler sentences: By 1899, the first batch of six locomotives of the Midland System was no longer reflected in the locomotive register. By 1904, all six of the Eastern System were gone from the register as well.