I once bought second-hand 4-volume text-book on marine-engineering, written for professional reference. This had a section detailing the unusual forms of the engines on these river-boats, vessels very much designed for the manufacturing facilities available, and the nature of the rivers and basic landing-stages. Looking at this photograph I wish I'd kept those books!

It was a simple but ingenious idea to make them both cargo and passenger ships by a flat, easily-accessible main deck for the cargo while the people occupied an upper deck supported on open frames. I'd not realised this until studying your photo.