Complex sentence: With ever more traffic going by rail, the canal's only significant weapon was low tolls: while this slowed the decline in volumes, it did so only by large reductions in income, and consideration was given to amalgamations with other canals.
Split into simpler sentences: With ever more traffic going by rail, the canal's only significant weapon was low tolls. While this slowed the decline in volumes, it did so only by large reductions in income, and consideration was given to amalgamations with other canals.