These too soon developed deep grooves, but could be more easily replaced than the stonework of the bridge.[1] While bridges could be constructed over relatively narrow canals, they were more costly on wide navigable rivers, and in many cases horse ferries were provided, to enable the horse to reach the next stretch of towpath. In more recent times, this has provided difficulties for walkers, where an attractive river-side walk cannot be followed because the towpath changes sides and the ferry is no more.[2]