Under-appreciated fact, this weight difference was one of the major reasons for switching from canals to railways, in their early days. The engineering needed

Under-appreciated fact, this weight difference was one of the major reasons for switching from canals to railways, in their early days. The engineering needed to hold up a train (along a hillside, never mind over a bridge) is much cheaper than that needed to hold up a canal, because a train is much lighter than all that water.