The other week, we had a helpful comment appear for this image (shown below) on our flickr site.

It suggested that these four vessels were steam lighters rather than barges as I had described them. Not being a ship expert, I had taken the description from the back of the photo and my understanding of the difference between lighters and barges was that they were one and the same.

The MDA Waterways Object Name Thesaurus that I sometimes refer to for describing items states that a barge is "a craft with a boat shaped bow and with flat (transom) rounded or pointed sterns. Almost all 14 feet wide or wider, the length can vary considerably." The definition given for a lighter is "generally a boat for transferring cargo from a large boat to another craft or the bank" and it marks lighters as belonging to the broader class of barges.

These definitions don't really get to the what the main difference is between these two terms for similar looking vessels. Instead the follow up comment from a fellow flickr user helped to clarify things by saying "that if it was unpowered and never left the canal, then it's a barge but if it was powered and could leave the canal, then it's a lighter." This ties in with other definitions for barges that I found in the dictionary which state that a barge is a long, large, usually flatbottom boat for transporting freight that is generally unpowered and towed or pushed by other craft.

As the four vessels in the picture clearly have funnels and are steam powered that would seem to make them lighters after all and not barges.