SFA, I looked as closely as I could at those beautiful steamers...really fascinating, they are huge too!
Here is a photo of a paddle steamer on the Mississippi River, probably a copy of the originals from the 1800's and Mark Twain time. Those in Wales have their paddle wheels UNDER the boat, while you see the Mississippi ones are built on behind! Maybe something to do with their size? These riverboats much smaller, must be!